British Submarine HMS Seal

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All the men aboard Seal now realized that their presence in the Kattegat had been detected and that the enemy would be searching for their boat. Proceeding at periscope depth, Lonsdale periodically checked the surface for enemy activity. Around 0800, he detected a group of anti-submarine trawlers sweeping the waters ahead of Seal, blocking her entry into the primary mining position. Lonsdale immediately chose to drop her mines in the first alternate position, which lay ahead and to one side of the area the trawlers were now sweeping. Minelaying commenced at 0900 and took only 45 minutes to complete. Lonsdale’s challenge was now to extricate Seal safely from the Kattegat and return to Britain.

The captain turned Seal around and began his hazardous homeward trip. The trawlers continued their sweep, and Lonsdale played cat-and-mouse with them. He reasoned that they had to stop when listening for underwater sounds on their hydrophones; otherwise the sound of their own propellers would drown out other underwater noise. Thus, whenever the trawlers stopped, so did Seal. The trawlers continued their sweep and gradually approached the sub, which was proceeding slowly on batteries at periscope depth. Around 1500, Lonsdale detected through the periscope another group of hunters, this one to the northeast. These were modern German motor torpedo boats, each carrying depth-charge throwers in addition to two torpedo tubes. Seal now continued her cautious game of evasion. Lonsdale’s goal was to evade both enemy forces until after dark, when Seal could surface and break for safety out of the Kattegat using diesel power.

The water depth was just over 100 feet, giving Seal no chance of going deep and running for it on weakening battery power. But one other possible evasive maneuver remained. Gambling that the torpedo boats and trawlers carried only hydrophones for detection, Lonsdale adjusted trim and settled Seal on a layer of salt water beneath the top layer of fresh water, at a depth of about 60 feet. The boat now slowly drifted with the current at a constant depth, rigged for maximum quiet.

As the submarine became silent, the terrifying sound of a wire scraping the starboard side of the hull could be heard. Soon the after hydroplanes jammed. However, before Lonsdale could do anything about this latest danger, Seal resumed trim, and the scraping wire seemed to have been cast off. It was now 1830.

Lonsdale ordered the crew to be served their evening meal, but at 1855 an explosion aft shattered this peaceful interlude. At first, Seal’s crew believed one of the surface ships above had dropped a depth charge. When no more explosions followed, however, another cause seemed more logical. Lonsdale reasoned that Seal had become entangled in a mooring wire for a German mine, which had created the scraping sound along the hull and temporarily jammed the after hydroplanes. As the sub gradually drifted with the current, the mine had been pulled into the hull and exploded. A quick damage survey revealed that all crew members were safe, but that the aftermost mining compartment had been partially flooded, with perhaps 130 tons of sea water inside the hull. Seal’s main ballast tank capacity was 380 tons; hence, Lonsdale and his chief engineer, Lieutenant R.H.S. Clark, calculated that Seal, now resting on the sea bottom at a depth of 130 feet, should have sufficient buoyancy to surface when her ballast tanks were blown. Lonsdale had the word passed that the submarine would attempt to surface after dark. In the meantime, all members of the crew were advised to rest and conserve the dwindling oxygen in the boat.

At 2230, Lonsdale made the first surfacing attempt. Seal rose forward, but her stern remained buried in the bottom mud of the Kattegat, held there by suction and the weight of seawater inside her hull. Lonsdale stopped both the engines and blowing tanks, and Seal gradually descended back to the seabed.

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Tags: 20th - 21st Century, Amphibious Operations, Historical Conflicts, World War II