While snorkeling at Ghajn Tuffieha (Malta) last summer, I encountered this type of fish. This fish wasn't intimidated at all by my presence thus it gave me a good opportunity to photography it even though with a fairly wide aperture setting on my camera.
Subject distance according to my Canon Powershot D10 was 370mm.
Remoras are primarily tropical open-ocean dwellers, occasionally found intemperate or coastal waters if they have attached to large fish that have wandered into these areas. In the mid-Atlantic, spawning usually takes place in June and July; in the Mediterranean, in August and September. The sucking disc begins to show when the young fish are about 1 centimetre long. When the remora reaches about 3 centimetres, the disc is fully formed and the remora is then able to hitch a ride. The remora's lower jaw projects beyond the upper, and the animal lacks a swim bladder.
Some remoras associate primarily with specific host species. Remoras are commonly found attached to sharks, manta rays, whales, turtles and dugong (hence the common names 'sharksucker' and 'whalesucker'). Smaller remoras also fasten onto fish like tuna and swordfish, and some small remoras travel in the mouths or gills of large manta rays, ocean sunfish, swordfish and sailfish.