 Open water fish are usually streamlined like torpedoes to minimize turbulence as they move through the water . Reef fish live in a complex , relatively confined underwater landscape and for them , manoeuvrability is more important than speed and many of them have developed bodies which optimize their ability to dart and change direction . Many have laterally compressed bodies ( flattened from side to side ) allowing them to fit into fissures and swim through narrow gaps ; some use their pectoral fins for locomotion and others undulate their dorsal and anal fins . Some fish have grown dermal ( skin ) appendages for camouflage ; the prickly leather @-@ jacket is almost invisible among the seaweed it resembles and the tasselled scorpionfish invisibly lurks on the seabed ready to ambush prey . Some like the <unk> <unk> have eyespots to startle or deceive , while others such as lionfish have aposematic coloration to warn that they are toxic or have venomous spines . 
