The Cockle Mark II folding kayak

The canvas craft could pass through submarine hatches, be assembled on deck, and be folded and hidden during daylight rests. Its low profile reduced visibility during a covert approach, while two seats let each crew share a heavy paddling and demolition load. Those advantages came with severe vulnerability to swamping, launch damage, and difficult handling in open water. The design therefore made the submarine insertion possible but transferred much of the mission's risk to the crews once they entered the Bay of Biscay.