I absolutely understand what you are concerned about. Divers, real actual scuba divers, have their visual spectrum so screwed up by water absorption with increasing depth that color rendering is not a high priority. Simply being able to see in the dark is what counts.
In tropical areas, with relative clear water, the criteria is significantly different from low visibility areas, like where I live.
(Note - photographers are a totally separate topic of discussion. CRI for them is not trivial.)
What we DO care about, a LOT, is the damn thing does NOT LEAK. THAT is the #1 priority. Everything after that is negotiable, not trivial, but if you light floods > it’s garbage.