The first time i knew i wanted to be a marine biologist was on my first deeper (below 20mt) dive of the advanced scuba diving course. In the Mediterranean sea around 25 mt of depth, the green algae and seagrasses disappear and sponges, gorgonians and red corals, dominate the landscape. This happens in a very precise and straight line, same as when you go to a very high mountain and you can see the end of the tree-line. No-one on the boat that day could explain to me why that phenomenon occurs. The moment i got back home and searched the answer, was the precise moment that i begun to be a marine biologist.