Ha! I found it! Its a m1767 French Grenadiere sword. Remember that in this time period, there were no specific models of naval swords for any nation. Officers carried whatever pleased their own taste. Brass hilt types were popular at sea as they retarded rust oxidation. There were several French naval patterns of swords from this period worn by officer types, which very closely resembled the common briquits worn by infantry and such, but no solid rules to what was required. Shorter bladed hangers and infantry swords were also popular as they were more efficient on crowded ship's decks and were less likely to get caught in the rigging when being swung.
Officers could basically choose which type of sword they wished to carry. In Annis' "Swords for Sea Service", the Maritime Museum identifies even cavalry types, baskethilts, foot officer's swords, etc, etc, going to sea.
One final postulation that has to be considered is whether this shipwreck was transporting military troops (i.e. non-naval, and thus a grenadiere sword) or whether your ship might have been a privateer (PIRATE!
), in which case, any manner of sword would have been carried.
Here's one from Dmitri's excellent site-
www.sailorinsaddle.com/product.aspx?id=1396