Symbiosis..

..between small fish and jellyfish appears to be protective for the small fish. I'm not sure what the gain is for the jellyfish, maybe access to fisheggs upon which it feeds, and actually the relationship can change when the small fish starts to feed upon the host, and therefore becomes a predator!
My favorite activity by the sea is snorkeling, for me it is as meditating as macro-photography. I can spend hours in the water, observing and learning, slowly floating on the surface with an occasional dive to have a close up. I'm not good at underwater photographing and my small actioncamera is not the top , but I still enjoy being able to document my swims!