Well I looked at sales history (ebay) of shipwreck pottery and saw some pricing. I searched also shipwrecked jar and those go for more. Some looked close to yours, but not quite. I would try posting also in the shipwreck forum. My guess it with the story make it worth something in the hundreds, but who knows could be worth quite allot if its rare to find that design and type in the condition yours is. On the down side it could be a modern replica, but it doesn't look it to me as I'm only going by what I've seen in museums and antique shops to compare.