The Groźny, a Soviet-built submarine chaser sunk during Warsaw Pact exercises in 1971, sitting at 16 metres off Jastarnia, and…The Groźny, a Soviet-built submarine chaser sunk during Warsaw Pact exercises in 1971, sitting at 16 metres off Jastarnia, and the Delfin, a former American training minesweeper of the same class Cousteau used, both in the shallow brackish water of the bay. Hel held out for a month after the rest of Poland fell in 1939 and the peninsula stayed a closed military zone for decades, which is part of why the seabed around it is full of hardware. Poland's deepest lake, Hańcza at 108m, is the other national dive site. Anchorage: Puck Bay behind the Hel spit is shallow, flat and protected, the standard cruising water of the Polish coast. Hazards: Low visibility, cold water, and a bay full of kite and windsurf traffic in summer. Plus