My friend Philippe Klinefelter, http://philippeklinefelter.com/, sent my the following interesting pictures and comments:
Mayan stone tools, primarily axe heads found in the coral, on the reef between Cozumel island and the mainland of the Yucatan. Displayed as the were found and removed from their watery resting place. Perhaps the boat was sunk in a storm. It appears to have been loaded with tool heads and arms.
Stone anchor perhaps the one lost on the boat above.