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I filmed the creatures below this August in the Mediterranean (specifically, the port of Fornells in Minorca of the Balleares). The images were taken from a boat moored just outside the harbor and flowting above a field of posidonia in case that is relevant.

There were many of them and they were whizzing about at high speed:

enter image description here enter image description here

This is to give you an idea of the scale. The jellyfish on the right was about the size of half a tennis ball.

enter image description here

They were a very strange sight since there were so many of them and moving so fast. You can see a video of them in motion here:

http://www.youtube.com/watch?v=GJCzjXALRJ0

The image quality is not very good but you can see how fast the things were moving. So, any idea what these are? I am assuming they are larvae of something or other but what?

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closed as too broad by Devashish Das, leonardo, J. Musser, The Last Word, MattDMo Jul 27 at 1:13

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