If you're looking for action and high octane stuff to do, this game isn't for you and you can start looking elsewhere for another game.
You can't really define this as a "Game", but what it offers you is hours and hours of relaxation, explore in a vast ocean, discover what it has to offer you in terms of surprise and beautiful scenary. There are "missions" you can do, but you tend to just rush through most of the magic on offer to achieve the goal. Which is completely the opposite of what this game is offering.
Once you learned the basics and acquire a few equipments, you'll just want to wander off by yourself and see as much as you can. You actually feel like you're exploring and words can't really describe the sensation of discovering something new for the first time and there are so many new things to find in the water.
All in all, this game won't appeal to everyone, and some hardcore gamers will even resent this game as this is another example of their favouriote past time being pushed to another demographic. But gaming isn't all about blowing the brains out of anything that moves, or clocking the fastest time on a track or beating the high score. If you have an open mind, this game will definitely broaden your horizon as far as what "games" can be.
I would definitely recommend this game, especially if you're the kind who always wanted an aquarium in your living room but can't afford one or too lazy to maintain one. Good stuff.