Okay, so I’m not just a know-it-all smart-ass, I’ll try to help a little. NO, I will not do the calculation, or even a back of the envelope estimate, but I will try to point you in the right direction and let you go dig up information if you really want to know.
Let us simplify to only floating ships, and ignore sunken hulks. I think this will make it easier, and the estimate will be so loose that I don’t think it will matter much. You can always tweak the values for a fudge factor.
Okay, so now you need some statistics and some reasonable guesses. These you will have to supply yourself.
Ws = weight of all ships, boats, submarines, watercraft, etc that are in the water all at one time, including their crews, payloads, etc. Make whatever assumption you want about how many there are, vs. how many are in dry dock. Any boat in dry dock is not in the water, so by definition it doesn’t count.
Ps = perimeter of shoreline on the ocean for the Earth. This should be some reasonable guess based upon all continents including Antarctica. You can pick low or high tide or an average or whatever you want.
Aw = area of the oceans. This is surface area, using the guidelines for Ps above. All ocean waters, ignoring lakes and rivers.
let Ww = the weight of all the displaced water.
I just said before that
Ws = Ws
so now you have some guess at the total amount of water that has been displaced, and thus is spread out to raise the shoreline.
Use the density of sea water (slightly less than 1) and then calculate the volume of water that is displaced. Vw
Now take that total volume of water and divide it by the area of ocean available to spread out. This will give you Delta height = H.
H = Vw/Aw
That will give you the total rise above a baseline that is caused by all the boats and ships, so you subtract H from the current sea level.
Now, given that shores are sloped and not equivalent at all, this can get funky for finding the difference, so you can for simplicity assume the shore is a cylinder of Perimeter = Ps and smooth perpendicular walls, and then H will show the water height difference.
Oh, in case you’re wondering, you could use Ps to help calculate Aw if you start with the amount of surface area of the entire Earth, and assume that cylinder or otherwise obtain a ratio for surface area land to surface area sea. Heck, you could probably estimate a 30/70 ratio, or 70% of Earth’s surface is sea, 30% land, and using the diameter of the Earth approximate your Ps and Aw.
Okay, you going to do the calculations and report back?