The chest is 100 lbs, the coins are 65 lbs, the rest of the stuff would be their normal weight. Then there is ~6 cubic feet of water. You maybe can lift it all the way to the surface (the chest will have 50 lbs effective weight underwater, the contents would have full weight), but I'm not sure how you load that on the boat without handling it to carefully drain the water without spilling the contents and then somehow lifting it. I guess you do the math and describe the actions and I'll see if it will indeed work.