Other cargo from prehistoric wreck sites near Salcombe, U.K., include these bronze axheads, designed to fit into a split in a wooden handle.
As with the axes' handles, nothing remains of the sunken Bronze Age vessels, so how they were constructed is a mystery.
The few surviving Bronze Age boats from northwest Europe were made of solid wood. But other evidence, such as rock carvings, points to boats made of animal hide stretched over a timber frame, said marine archaeologist Dave Parham. (Related: "Viking Shipwrecks Face Ruin as Odd 'Worms' Invade.")
Such vessels would have been more than capable of crossing between France and Britain or transporting the 190-pound (86-kilogram) load recovered at the newfound wreck site, Parham said.
"It's a modern concept that you need something big to go to sea," he added.