Tiny coral worm...

... on the propeller of a small boat. The little worms are no more than a few millimteres in width. For Tiny Tuesday, with thanks to Incredibish for hosting this month.

Coral worm can be quite a nuisance to the underside of boats if it is left unchecked.  In some cases where the boat has been left moored without use for a long time, it can completely cover the small propellers and render them useless or damage the engine. I have an example in the extras of the whole propeller and another of a part of the hull. Boatyards are such fascinating places.