I did some research and found eel goby's, eel snakes, worm eels, snake eels etc etc... there are litterally hundreds of different species of them along with eels in general I have seen pictures of Conger eels that resemble this pic all the way to Snake eels and eel blenny's. The issue IMO Is that first the pic isnt the best and second this is most likely a juvenille specimine and difficult to identify because all of the comparsons shown are adults. Worm Eels was another possibility, all of these species range from brackish to marine waters and also found on reefs. I saw a Slender eel goby that was very close, but pictures are hard to come by. Conger eels are found in the Atlantic but are also found in all temperatures and depths. Although I doubt you have one, you can see a pic that in a way resembles your....ummmmm, fish type thing. FWIW If it is one they can reach lengths of 8ft... LOL.
The last pic is the conger, also you can look up, Slant lip eel shown on the next post and eel blenny's which I didnt have time to snag a pic of, but also could be a possibility. Hope it helps..
