There could be trumpetfish in this area (I know I've seen them in and around the Dominican Republic). But, in all honesty they would really pose a small biting risk to swimmers. They are close relatives a seahorses and pretty docile from my experience. They have small mouths and usually ingest phytoplankton, but larger ones could take in a small blennie I suppose. They hang out in a vertical suspension position among the tall sea grasses, so if someone stepped accidentally where they were spawning they might take a nip at you, but I don't think it would amount to much. I believe the true culprit is most likely Palometas as mentioned above. I'm definitely going to check this out in March first hand.