"Quick! get the human film! those people want to learn about us, they need to come down here themselves. Let's show them stuff they already know! hehehehehehe (high pitched dolphin sound)"
But how exactly would one train a dolphin to track an enemy ship without being noticed, then actually get decent shots of it from underwater...?
Looks like a research camera used by marine biologists and the like to study the ocean without using expensive submarines and all that.
I guess the dolphin just decided to have some fun with it, lol.