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I was snorkeling on Mexico beach and I looked down and saw this guy swimming around me. I caught him and put him in my tank. I was sure it was a remora or shark sucker but it has no suction.
It's a little tricky to tell from your photo, but I am pretty confident it's a juvenile Malacanthus. Do an image search on "Malacanthus juvenile" and see if it looks close.
The other fish that comes to mind (and from a completely different family, but one more closely related to remoras) is Rachycentron - cobia or black kingfish. Again, do a search on Rachycentron juvenile to see if it looks close. This site has some photos of small juveniles: ScienceFish - Cobia Hope these two guesses help.
Yes, I realised you were not in the Indo-Pacific, but there are malacanthids still in your area. On seeing your new photo, I'm now leaning more towards my second guess.