caribbean reef shark (carcharhinus perezi) sleeping in a cave in jupiter, fl. until recently, shark experts believed all sharks, except nurse sharks, had to swim in order to breathe and survive. it turns out several species, including the caribbean reef, bull, and lemon, among others, can remain perfectly still and pump oxygen rich water through their gills. date: 21.10.2008 ref: zb1050_122586_0001 compulsory credit: oceans-image/photoshot