I have some ideas for ways that you can help the endangered animals, like the manatee. People can set up sanctuary areas that are just for the manatee. People will not be allowed to bring in boats or jet skis that can damage the habitat or hurt the animal with their propellers. Another idea is to have "eco-tours" where you set up a way for people to visit the animals and habitats. The money that is raised could be used to help the animals. If people know more about the animals they might not want to hunt them or harm them.
I'm not sure what other water animals are endangered but you could probably get that information at your school library or on your computer.
Grace