The barnacles last season looked a bit bigger and more plentiful than normal. Anyway, when I was scraping them off the hull and rudder the other day I noticed a few small patch of what I took to be coral forming on the hull. Now, I only call it coral because that's what I was told it was was by my mum and dad about sixty years ago - that kind of bone like growth that you can see on rocks and shells.
Anyway, I noticed this growing on a small motor boat;

What is it - coral or what? Have to say that although I don't regard myself as being especially unobservant, I don't think I can recall seeing any on the hull before.