Interesting relationships

The sea is full of interesting relationships, some symbiotic, some parasitic, some for convenience, and some we have yet to understand.

This one is interesting, the little red fish are probably using the sea urchin’s spines for protection, but another possible explanation is that they were playing in the eddie currents caused by the water washing over the spines. Indeed there was a lot of current (and surge) on this dive, off Dirty Rock in the Cocos Island, and eddie currents would have formed around the spines of this sea urchin. I am not sure the sea urchin was deriving anything from this (apart from a cleaning of its spines), but the fish seemed to be enjoying it. Most of the sea urchins there had the same thing going on, and there were a lot of them there! The scale is a little deceiving, the spines are actually about 8-12 inches across, definitely a hazard for the unweary diver.

This dive in Dirty Rock was one of the more challenging dives we went on, there was a current and lot of surge. While this was a minor problem at 80 feet, you still had to use your (gloved) hands to maneuver along the bottom, the surge was a pretty major problem for the safety stop at 20 feet and you were bobbed around like a cork in a storm. It was a blast!

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