Oscar the sea turtle was a frequent visitor near the dock in Thailand where Grant Stirton's tour company stored their boat. Stirton jumped in the water to snap the turtle's portrait.
Fusiliers swim past gorgonians off Thailand's Similan Islands.
A reef manta ray swims at the western ridge of Koh Bon Island. Sightings of these majestic animals are becoming less frequent with every season, Stirton said, as they are targeted for their fins.
Priacanthidae, or common "big eye" fish, are nocturnal feeders. Their large eyes allow them to see better at night.
Butterflyfish swim through sea whips at the Koh Tachai pinnacle near Tachai Island. The shapes and markings of the fish closely resemble the shapes and lines of the surrounding coral, making them very difficult for a hungry predator to pursue at high speed.
A couple of lionfish hunt for small fish. Although their spines are very poisonous, lionfish are very calm and safe if approached gently, Stirton said.
Red-toothed triggerfish get their name from the small dorsal fin that resembles the trigger mechanism of a gun.