Exactly what I mean, underwater caches that are accessible by a basic dive without scuba gear are much more prevalent than scuba gear caches yet the relationship is not reflexive. For example you can label a scuba cache and underwater cache but you cannot (or should not) label a basic dive that doesn't require scuba gear a 'scuba gear' cache. It would make much more sense, if it's such a huge problem to add one more icon for an underwater cache, to change the scuba gear icon into an underwater icon and then have the description detail whether it required gear or not, this would make it MUCH easier to locate underwater caches.
The problem with PQing 'may require swimming' is there are A LOT of caches that may require swimming but are not underwater. It would take a lot of work to filter through these. Having a diving/underwater cache that doesn't require scuba gear is a much more unique situation/attribute worthy than the other examples listed above which would justifiably be labeled with icons such as 'may need to climb' or whatever else as there is not as big a difference between those as there is between 'needs scuba gear' or 'may require swimming' and 'underwater cache' (no scuba gear required).
For example if you were to PQ for 'may need to swim' attribute you are likely going to pull hundreds of caches that may require swimming to an island or something of that nature, there are TONS of them, to go through that entire list looking for the underwater caches would be unnecessarily time consuming and difficult when there could just as easily be an icon added for an underwater cache (or at the very least have the scuba icon changed to a general underwater cache as 'scuba gear required' is much too specific and there are sooo few of these caches that even exist).