I do not think it makes sense for shipwrecks to have regular chests. Perfectly upright despite the crash? I think it looks much better and makes more sense if they were barrels instead.

Honestly, that is the way it should have been from the start, but I guess it makes sense since while shipwrecks were added in 1.13, barrels were not added until 1.14, and I guess they forgot to go back and fix it.

This pack also removes those doors that create air pockets, but if for some reason you dont want that then the version with only the chests to barrels part is here: Shipwreck Barrels instead of chests (NBT) Minecraft Data Pack (planetminecraft.com)

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This change is included in my RL Megapack posted here: Aceplante's RL Megapack, but I also wanted to post it separately in case anyone wanted this specifically.