To find scuba caches just set your filters to terrain 5, scroll around the map, and read descriptions on likely looking spots to find any that actually require scuba rather than snorkel/wading, or just a boat to get there. I see at least one off Cayman Brac and 2 off Roatan.
I’m sure there are more scuba earthcaches to avoid the difficulties of physical ones, but those are fun too. I logged one on Little Cayman last week. Still needed to dive to answer the earthcache question. (You might be able to get the answer from a local dm, but it’s a nice dive.)
Underwater caches will typically provide enough hint and description so you don’t need GPS to find, at least not once you’re underwater.