When I was a kid my family used to fish in Monterey Bay. My dad would rent a small 12-foot boat and we'd head out offshore a ways. Once we were on our way out and the water around the boat suddenly turned pink. We were in the middle of a jellyfish swarm. A bizarre sight when you're right there on top of them. It took several minutes to get through it. The spray from the boat would sting as it landed on our skin. I wouldn't want to be in the water in the middle of one of those.