You can suggest all you want...
They sign up on the same day.
Their posts strongly refer to their own sites.
They like each other's posts.
They both follow each other.
Born on the same day.
See here:
Hai guys this is Information how to settings GoPro when Diving
Planning Your Drift Dive
Manta Rays Facts - Scuba Center Asia
So, yeah, no, thanks for the suggestion but just no.
Sounds to me like a dive op that decided they want to have an online presence. They and a couple of folks from their shop sign on. They post some on scuba board to generate some interest. Something I have seen from several of our regular posters. They run a shop/instruction business and post a lot. Clearly it is advertising but in a positive way and adds to the board.