Every diver knows the feeling: the rush to grab a marine-ID book or placard after a critter-filled dive to see exactly what you encountered on the reef. If you pore over those books long enough or log enough dives, identifying marine life becomes second nature.

But it can also be tricky. Sometimes, the traits separating entire species are marginal. Want to put your marine-ID skills to the test? Take our quiz above for a shot at bragging rights among your dive tribe.