We were lucky enough to spot some tarpons while inspecting a sunken barge at about 110 feet. Seeing them made me realize I know very little about these fish, spurring a bit of fun internet reading.
Tarpons are members of a group of fish known as elopomorphs that also include bonefishes and eels. One cool thing about elopomorphs is that all members of this group of fishes all have leptocephalus larvae, which look like really flat eels with glassy transparent bodies. If flat mini eels with see though bodies sounds delicious to you, eel leptocephalus (or elvers) are considered a delicacy in the basque region of spain.
There are two species of tarpon, with only one (Megalops atlanticus) found in the atlantic and caribbean (that is the species you see in the pictures above). They can grow up to 8 feet in length, though most tarpons average between 2 and 4 feet. I had always assumed that these were pelagic fishes that would rarely come near shore, but I was apparently wrong. Instead, tarpon live in brackish, fresh, and saltwater.
Additionally, they have a bizarre swim bladder that functions as a respiratory organ. While this is not uncommon in fishes, tarpons are the only pelagic teleosts to use their swim bladder this way. In fact, if juveniles cannot come up to the surface to breathe, they will drown. Adult tarpons keep this air breathing function and use it to augment oxygen uptake during exercise, and this may also explain why tarpon can often be found in waters with a low oxygen content. In Curaçao, a school of four individuals are apparently long-term residents of the sunken barge.
As a side note, the barge was carrying a cargo of cars and a crane when it sank. Today, you can see this now decayed cargo strewn about the ocean floor.