In my current (also first) extended Survival game, I've visited three shipwrecks, once without enchantment and twice with a Potion of Water Breathing in effect.  I plundered all three.  Despite this, the "Ahoy!" achievement has not unlocked.  ("Echolocation" and "Free Diver" have unlocked, though.)

In the process of doing that and other things, such as harvesting a few stacks of kelp, I've rowed around quite a bit of water.  The "Sail the 7 Seas" achievement shows 0% progress in the XBox Console Companion.  Other achievements with partial progress, like "Hot Tourist Destination", do show progress toward completion.

I can provide a zipped save file, or other files, upon request.  The game was started in 1.14,  and the problems described above occurred under both 1.14 and 1.16.