If you're a "reefer" like me, you'll absolutely love it. And by "reefer," I mean "a saltwater-enthusiast who likes to have a piece of ocean in their home." I have three saltwater tanks and they are my world.
The game is very "chill" and a great game to play when your arm is sore from playing Tennis Wii The graphics are very good and true-to-life, and while it's not all action-action-action, it's interesting, educational, beautiful and relaxing.
If you have any kids that like to come over and play -I have two nephews and one niece- it's definitely a cool game to have. I'm 21 and I love to play it once or twice a week, when I need something less action-filled.
You do have goals, but no set times to achieve them, and there are things to unlock and discover.
It's already been said, but I'll second (or third) that if you're not sure you'll like it, rent it first. I think you should at least try it. It may surprise you!