HNLMS Tonijn ('Tuna') was laid down at the Wilton-Fijenoord shipyard in Schiedam, Netherlands on 26 October 1962 and launched on 14 June 1965. Commissioned on 24 February 1966, Tonijn was the fourth and final Dolfijn-class diesel-electric submarine built for the Royal Netherlands Navy between 1954 and 1966. The Dolfijn-class boats were the first submarines built in the Netherlands following the Second World War and they formed the backbone of the Royal Netherlands Navy's Submarine Service for most of the Cold War.
Tonijn and the other Dolfijn-class boats were known as 'three-cylinder submarines' because their design consisted of three separate pressure hulls stacked in a pyramidal manner, linked by hatches, and enclosed by an outer hull casing. The three-cylinder design was the brainchild of Dutch engineer Max F. Gunning (1895-1972). The design improved the stability of the submarine, allowed it to dive deeper than other contemporary submarines (200 metres/660 feet), and permitted submerged operations for longer periods of time than previous Dutch submarines. In the three-cylinder design, the diesel engines, generators, electric motors, and batteries were housed in the lower two cylinders and the crew living and working areas were in the upper cylinder.
Although the design for the Dolfijn-class boats was finalised in the late 1940s, the cash-strapped Dutch government did not immediately authorise construction. After a re-design to lower the cost of the submarine, the government called for tenders in August 1950 and awarded a contract to the Rotterdam Drydock Company to build four boats at a price of 12 million Dutch guilders each. Construction of the first two boats began in 1954, and HNLMS Dolfijn and Zeehond were commissioned in December 1960 and March 1961, respectively. In light of the development of nuclear propulsion technology, the Dutch government paused the construction of the remaining two Dolfijn-class submarines in order to research the feasibility of adopting nuclear propulsion for these boats. In the end, nuclear propulsion was rejected by the government and the last two submarines were built with conventional diesel-electric engines, commissioning in November 1965 (Potvis) and February 1966 (Tonijn), respectively. The gap between the first and last pair of boats has led some to label the latter the Potvis-class, though the four submarines are virtually identical.
In service, the Dolfijn-class boats were principally tasked to defend against Soviet submarines. Their stealth and quiet operation made Tonijn and her sisterships ideally suited to collect data on vessels of the Warsaw Pact navies. To this end, covert patrols were frequently undertaken in the northern Arctic Ocean and the Mediterranean Sea. In wartime, the Dolfijn-class boats would have been assigned to attack enemy surface vessels, submarines, and merchant ships; lay mines; gather intelligence; insert and retrieve agents from enemy territory; rescue downed pilots; serve as radar pickets for the Dutch fleet; and defend Dutch ships against enemy submarines.
Over the course of her career, HNLMS Tonijn took part in numerous routine patrols and port visits, including to Germany, Ireland, Norway, Scotland, and Belgium. A fire in the port and starboard engine rooms in September 1979 led to a refit in Rotterdam. This included replacement of Tonijn's original 1,400-horsepower MAN diesel engines with 2,200-horsepower SEMT-Pielstick PA4 diesel engines.
The four Dolfijn-class boats were decommissioned between 1982 and 1992, with Dolfijn, Zeehond, and Potvis being scrapped. HNLMS Tonijn is the sole survivor of the class, having been decommissioned on 10 January 1991 and preserved as a museum ship at the Royal Netherlands Navy museum (Marinemuseum) in Den Helder since the summer of 1994. With Tonijn now sitting in a cradle on land, visitors are able to enter the submarine via the forward torpedo loading hatch and tour the entire length of the upper pressure hull's operational and accommodation spaces; the lower two pressure hulls containing the propulsion machinery compartments remain closed to visitors for safety and accessibility reasons.
Specifications: HNLMS Tonijn (S805)
Displacement: 1,510 tons (surfaced) / 1,830 tons submerged
Length: 78.3 metres (256 feet 11 inches)
Beam: 7.8 metres (25 feet 7 inches)
Draught: 5 metres (16 feet 5 inches)
Propulsion: 2 x MAN 4-stroke, 12-cylinder diesel engines generating 1,400 horsepower (as commissioned), replaced in 1979 by 2 x SEMT-Pielstick PA4 high-speed 4-stroke diesel engines generating 2,200 horsepower; 2 x electric motors generating 2,200 horsepower
Speed: 14.5 knots (26.9 km/h; 16.7 mph) surfaced / 17 knots (31 km/h; 20 mph) submerged
Diving depth (theoretical maximum): 350 metres (1,148 feet)Diving depth (test/operational): 200 metres (660 feet)
Armament: 8 x 21-inch torpedo tubes (four in bow, four in stern) with a maximum load of 16-22 torpedoes (Mk 8 initially, Mk 37 later)
Complement: 67 (one commanding officer, six officers, 13 chief petty officers, 20 petty officers, and 27 ratings); capacity for up to 71
Photos taken 30 April 2026
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| HNLMS Tonijn sits in a cradle next to the grey entrance building of the Marinemuseum in Den Helder. |
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| Tonijn's bow, with a torpedo halfway out of one of the starboard tubes, hangs over the canal running across the north side of the museum property. The large protrusion under the bow houses the submarine's active and passive sonar arrays. |
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| A view from the ground next to HNLMS Tonijn. At the time this photo was taken, the submarine's starboard side was in the process of being repainted, with orange anti-corrosion paint daubed over the hull prior to the application of the coat of black paint. A footbridge and staircase leads visitors from the museum building to the upper hull, where a hatch allows access inside the submarine. |
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| Looking down Tonijn's starboard side from the bridge linking the submarine to the museum building. Sprouting from the top of the fin are the radar and radio masts, the navigation and attack periscopes, and the snort mast. The outer hull houses the boat's six main ballast tanks. |
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| A ladder leads down into the forward torpedo room from a hatch on the submarine's hull. Torpedoes were loaded and unloaded via this hatch. |
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| A museum guide talks to visitors in the forward torpedo room. His left foot is resting on one of the 21-inch torpedoes that were stored on and under the deck in this compartment as reloads after those in the torpedo tubes had been fired. |
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| Fitted with 24 folding bunks, the forward torpedo room doubled as accommodations for petty officers and ratings. The lower bunks, stripped of their mattresses, also served as tables. An orange survival suit hangs on the left, to be used by submariners needing to escape through the emergency hatch at the top of the ladder between the torpedo tubes. |
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| A closer look at the four 21-inch torpedo tubes in the forward torpedo room. A maximum of 16-22 torpedoes could be carried aboard the Dolfijn-class submarines, split between the forward and aft torpedo rooms. Tonijn initially carried Mk 8 torpedoes, later superseded by Mk 37 torpedoes. The torpedo tubes could also be used to launch sea mines. |
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| Some of the two-tiers of folding bunks in the forward torpedo room. Green curtains provide a degree of claustrophobic privacy for those sleeping in this compartment. |
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| Sinks mounted on the port side of the forward torpedo room, used by the sailors for washing. |
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| The watertight hatch leading aft from the forward torpedo room. In the event of flooding in a compartment, such watertight hatches would have been sealed to prevent the rest of the boat from becoming swamped and possibly sinking. |
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| One of Tonijn's toilets, located on the starboard side just aft of the forward torpedo room. The submarine's toilets were flushed with salt water. Sewage was collected in a wastewater tank and, when full, emptied at night. |
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| A shower cubicle with sink. Depending on the availability of fresh water, each crewman was allowed to take one shower per week. Each man's shower time was restricted to a few minutes. |
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| Looking aft, down the passageway that runs from bow to stern. |
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| A large stainless steel kettle sits atop an Electrolux heater in the officers' pantry on the starboard side of the passageway, across from the wardroom. Ingenious metal bars cradling the kettle would keep it from sliding off in case the boat dived or rolled in rough seas. |
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| The wardroom, where Tonijn's officers dined and relaxed when off duty. With the exception of the captain, the officers also slept here, in bunks at the other end of the wardroom. |
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| The captain's cabin. The submarine's commanding officer was the only member of the crew with a private cabin. The cabin measures a mere 1.9 metres (6.2 feet) long by 1.5 metres (4.9 feet) wide. It was tiny compared to the captain's cabin aboard a frigate or destroyer. |
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| Looking forward through the watertight hatch leading from the control room to the officers' accommodation space. The control room is the nerve centre of the submarine and is the largest compartment in the boat. It was divided into a series of adjacent operational spaces: the radar/electronic warfare cabin, the sonar cabin, battle room, submerging room, radio cabin, and auxiliary room. |
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| The radar/electronic warfare cabin. When the submarine was surfaced, the radar was used for navigating during bad weather conditions. Radar was used to scan for the presence of ships and other objects nearby. Tonijn's electronic warfare equipment was used to intercept and analyse the radar signals of vessels and aircraft. |
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| The sonar cabin. Sound was the only way to monitor the submarine's surroundings when operating submerged. One of Tonijn's important tasks during the Cold War was recording the sounds emitted by ships and submarines of the Warsaw Pact navies for intelligence purposes. This explains the large number of recording devices fitted here in the sonar cabin. |
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| The battle room, from where the submarine was commanded when surfaced or submerged. The centre of the room is dominated by the navigation periscope and the well into which it retracted when submerged. The periscope is flanked by the helm position, a charting table on which the boat's course was plotted, and the diving control position. |
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| A closer look at the navigation periscope, identifiable by its twin eyepieces. This periscope was used by the captain or officer of the watch to monitor the boat's surroundings when surfaced or submerged at periscope depth. |
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| The attack periscope. With its slim, tapered upper head designed to reduce wake disturbance, the attack periscope was used in combat to spot targets, calculate range, and gather precise firing data while minimising the risk of detection by enemy ships or aircraft. |
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| The helm position, at the forward port side of the battle room. The crewman posted here controlled the submarine's rudder and speed. |
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| The submerging room, at the aft port side of the battle room. It was from this station that the submarine could dive, maintain a desired depth, or surface through the use of valves controlling the six main ballast tanks. The submarine submerged by filling the ballast tanks with seawater. Once submerged, steering handles controlled by crewmen seated here moved the front and rear depth planes on either side of the outer hull in order to steer the submarine up or down. |
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| The control room's bulkheads are covered with gauges, levers, valves, pipework, and other vital machinery needed to operate the submarine. |
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| Controls for the ballast tanks. To surface, compressed air held in cylinders blew the seawater out of the ballast tanks, causing the submarine to become buoyant and rise. |
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| Continuing aft from the control room. |
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| The radio cabin, which played an important role during submarine operations. When surfaced or snorting, radio messages were received or transmitted; however, transmitting was very limited, as it could easily reveal the position of the submarine. |
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| The auxiliary room, where the submarine's main electric motors were controlled. Tonijn always sailed using electrical power, even when her diesel engines were re-charging the batteries when surfaced. The boat's speed was regulated using large levers which activated electrical switches. |
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| The auxiliary room is the furthest aft section of the control room. The crew here were responsible for monitoring and controlling the boat's batteries and electric motors. |
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| Re-charging the batteries, located in the submarine's lower hull cylinders, was also controlled from here in the auxiliary room. |
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| The watertight hatch leading aft from the control room into the next compartment, housing the chief petty officers' quarters and the galley. |
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| A wooden sign mounted in the passageway outside the chief petty officers' mess, nicknamed Gouden bal ('Golden Ball). |
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| The 'Gouden bal' was where the submarine's chief petty officers slept, relaxed, and ate their meals. The mess has 20 bunks. |
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| The galley, in which meals for the officers and ratings were prepared. |
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Tonijn's menu for the week of 24-28 June 1968 featured a wide variety of items to keep meals interesting for the crew:
- Breakfast: white & brown bread, cold cuts, oatmeal, cheese, sweets, boiled eggs, scrambled eggs with tomato, English breakfast.
- Afternoon: tomato, pea, or vegetable soup, noodles, meatballs, Dutch East Indies dishes, fried cod, pork belly, brown beans, fried and raw onions, pork cracklings, fried eggs, pickled vegetables, green beans, apples, apple sauce, boiled or mashed potatoes, rice, carrots, peas, hollandaise sauce or gravy, mixed salad, custard, oranges.
- Evening: noodle soup, steak with mushrooms, white & brown bread, cold cuts, cheese, sweets, macaroni bolognese.
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| Another watertight hatch leads from the galley to the aft torpedo room. Note the large urn on the galley counter to the right of the hatch: a plentiful supply of fresh coffee helped maintain the morale of the 67 men serving in the submarines's tight confines. |
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| A shower cubicle with sink in the aft torpedo room. |
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| Sinks and pantry storage in the aft torpedo room. |
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| Like the forward torpedo room, the aft torpedo room has four torpedo tubes and accommodates 20 ratings. The only difference from the forward torpedo room is that the aft torpedo room also served as a dining room. |
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| Folding bunks mounted on the bulkhead. |
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| The aft torpedo room is fitted with folding bunks and free-standing tiered bunks in the centre of the room to accommodate the 20 junior ratings who lived here. |
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| The aft torpedo tubes, numbered V to VIII. Like the forward tubes, these also fire 21-inch torpedoes. Reloads are stored on or under the deck of the torpedo room. |
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| The torpedo tube status board, mounted from the deckhead in between the four tubes. Switches and indicators control the flooding and pressurisation of the tubes. The firing levers are located on either side of the status board. |
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| A look at the space between the two sets of torpedo tubes. |
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| The aft torpedo loading hatch on the upper casing, now the exit for visitors. |
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| A Dutch flag flies from the jackstaff at the stern of HNLMS Tonijn. |
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| Looking forward at Tonijn's upper hull and fin, pointing north towards the North Sea. |
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| Disembarking Tonijn via the platforms and staircases that return visitors to the ground. |
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| The port side of Tonijn, as seen from the ground. Located at the aft end of the fin, topped by a rounded grey cap is the snort mast. The telescopic snort mast could be extended up to eight metres (26 feet) while sailing submerged at a shallow depth, allowing fresh air to be inhaled for the diesel engines and exhaust gases to be discharged. Not only did snorting allow the batteries to be recharged while sailing submerged, it also partially refreshed the air inside the submarine. The cap on the top of the snort mast is a head valve that blocked seawater from entering the snort by automatically clamping down when a wave washed over the mast. |
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| Looking up at Tonijn's twin five-bladed propellers, rudder, and aft diving planes. |
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| HNLMS Tonijn, high and dry on a cradle next to the Marinemuseum. |
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| A final look at HNLMS Tonijn on display in Den Helder. |
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