On March 30, while on the Grand Bank, in latitude 40 10, longitude 33, they discovered an immense live trunk turtle, which at first thought to be a vessel bottom up. the Schooner passed within 25ft of the monster, and those on board had ample opportunity to estimate it1s dimensions by a comparison with the length of the schooner. The turtle was at least 40ft long, 30 ft wide from the apex of the back to the bottom of the under shell. The flippers were 20ft long. It was not deemed advisable to attempt its capture. The trunk turtle could be a Leatherback turtle, they never stop growing as long as they live.

So it`s probable, but not likely.