Great place to go on a sunny day and many things to do on the island. They have canoeing, kayaking, stand up paddle boarding, biking, and many other activities which I don't remember off the top of my head. They also have a lot of space to lounge and a lot of beach area. There is a path that goes around the whole island so you can spend a good amount of time biking / going around the island.
Great place to bring the kids as well because they have the small amusement park with a petting zoo, pony back riding and other activities and foods kids love.
There's a ferry you have to take which is like $7 round trip if you're a student. It also has a great view of the city and is an enjoyable trip to and from centre island.