One of the highlights of observing fish as a diver is to find a dragonet. Dragonets are small bony fishes which live between corals or in the sand and are found in tropical, sub-tropical and temperate oceans. There are 191 species of dragonet currently listed on Fishbase, including the well-known mandarin fish.
Mandarin fish, Synchiropus splendidus, hide in coral rubble and mate at night time above the corals for just a few seconds, releasing fertilized eggs into the water. Male competitors will sometimes engage in a display contest to gain mating rights; showing off their sizes via their outstretched fins.
The video below showcases the unusual locomotion used by some sand-living dragonets. They tend not to swim, as it uses more energy than crawling, and may prefer crawling to also reach their prey, tiny invertebrates, more easily and without being seen. They use the spines of their pectoral fins, almost like fingers, when crawling. When they swim, the pectoral fins (now transformed into crawling appendages) aren’t of much use anymore, and so they mainly use the pelvic fins for swimming.