Endless Ocean is like a chill pill to put your mind in meditation mode. It's not a game so much as it is a simulation of scuba diving in blue, tropical waters. All you do is swim, pet fish and befriend dolphins and penguins.
When you pet fish, you reach out and rub their little bodies. You know they enjoy this, because magical sparkly lights float around their contented heads.
You have a job to carry out, but only tangentially. The whole reason you're able to afford this lackadaisical life is that some charitable foundation is paying lucky you. Your mentor is a marine biologist who hangs out on your boat.
If there's a goal, it's simply to move the boat around to lagoons and deeper waters, and conduct topographical inspections on behalf of the charitable organization. But you can also just sit on the deck and watch the calm waters, the green islands and the blue skies bobbing in front of your lazy eyes.