Bubbles
Fig. 2: The air from the divers in the cave is creating a curtain of bubbles. Looks like diving in a jakuzzie. — Sea & Sea DX-8000G, Koh Ha, Thailand, December 2007 RICOH Caplio GX8; Δt=1/470 s; f=5.8 mm; f/4.7; ISO 400; 23 December 2007 05:34:56