Ms Frizzle and her class will give them lots of information and open doors to further exploration. Although tides and waves and the ocean floor are interesting, it's the life in and around the ocean that fascinates most of us. Again it's Simon to the rescue. Even kids who can't read the text of any of those books can gain lots of information by carefully perusing those photographs. They need structure in which to record their information so it's time to get graphic.
Food chains are interesting in any eco-system and the food chains in the ocean are many.
Have the kids start making large images of single sea animals on cardboard circles or pizza boards. Place their creatures on the bulletin board and have kids find out what each one eats. If the prey is already on the board, connect it by making an arrow from predator to prey. If it isn't there, draw it and then connect. Soon there should be extensive webs.