DiverDave: On every trip to Cocos that I made, I saw dolphins, mantas, tunas, wahoos, eagle rays, sometimes mobulas, marbled rays, and and at least 6 different species of sharks: scalloped hammerheads, enough to fill your field of view, white tip reef sharks, silvertips, Galapagos, silkies, and black tip. And if you're lucky, maybe whaleshark. I didn't see any in September 2004, nor in June 2005, but had over 12 sightings on our last trip in July this year. Tigers have also been seen but they are very rare for Cocos.
Then there are the big schools of Big Eye Jacks, barracudas, different types of snappers, and creolefish, along with all the rest of the reef fish.
Night dives are available in protected areas, and the most celebrated one is the one on the back side of Manuelita Island where literally hundreds of white tip reef sharks congregate and travel like a wolfpack hunting for reef fish.
Yes, the ride out can be murder, and yes, the diving here, with the currents, thermoclines, and sometimes rough surface conditions is best suited for advanced divers - but it is extremely rewarding. Again, I do not know what the conditions and the diving are like in February, which is why I suggest that you check on the boats' trip reports.
We were also very fortunate to be able to snorkel with a Mother Humpback and its calf. That's as far as what I've seen - but there is a whole lot of other stuff that has been seen that I have not yet seen. In Cocos, anything is possible. That's as far as the big stuff.
