Orange-fin anemone fish (Amphiprion chrysopterous Cuvier) in aurora anemone (Heteractis aurora), Tetons, South Save-a-Tack Passage, Namena Island, Fiji

Aurora anemones are about the size of a salad plate, and the tentacles are dense and short.  There's really no way your standard two-stripe anemone fish can get himself much protection amongst the tentacles.  So, when frightened, the fish dives right into the mouth of the anemone, like you see here.

There was a nice aurora anemone at E6 in 1998, and I tried to get this shot then, but the fish was too confident, and when I got to the right distance with the 105, he wouldn't hide in the mouth.  I guess, E6 being the high-profile dive site that it was before the 2000 coral bleaching, the fish just got so many people sticking cameras in his face that he wasn't very frightened.  However, this fish dived right into the mouth when he saw me coming. 

Nikon F4, 105mm f/2.8 AF Auto Micro Nikkor, TC-14 tele-extender, PK-14 (14mm) extension tube, Aquatica Housing, 2 Ikelite 200 strobes, f/22, Fuji Reala 100.