What is that fog horn / hooting fish noise?

[sarahnorthway]

I've been visiting a coral reef in Bocas del Toro, Panama, and keep hearing a very odd noise every few minutes. It sounds like someone's cell phone buzzing, a deep double fog-horn-sh "mehhh-mehhh".

The reef is close to the surface and you can hear the noise above the water too. It happens at all times of the day and is especially noticeable at night (while swimming in the bioluminescence). The sound moves around so I figure must be some sort of fish looking for a mate, but I haven't been able to find the source. Locals guess it might be an octopus or needlefish but can't find any site that backs this up. Does anyone have a clue what is making this noise?

 

[dumpsterDiver]

croakers.. ?

 

[sarahnorthway]

croakers.. ?

Ooh, thank you, this could be them! I could only find an audio sample from the Atlantic Croaker, which I think we're too far south + inland for, but it's kind of similar to what we're hearing:
http://www.dosits.org/files/dosits/croaker48-2.mp3

I haven't seen any Spotted Drums here (Spotted Drum - Wikipedia, the free encyclopedia) but it might be a Reef Croaker (Odontoscion dentex, Reef croaker : fisheries)