Could this be Firestorm, part of the "Caretaker" trilogy of books by David Klass?
The main character does quests (something to do with the ocean) and has a girlfriend called P.J.
His mother is not his mother. His father is not his father. But if
Jack hadn't broken the high school rushing record that night, he never
would have known and nothing would have changed. He'd just be going
out for pizza, playing football, trying yet again to score with his
girlfriend, P.J. But he did break the record. He appeared on the news.
And now they've found him. Jack plunges into a space-time-bending game
of survival with no way out. The rules are shrouded in secrets. But
one thing he learns fast: Trust no one. After centuries of abuse, the
earth is dying, and it's up to Jack to reverse the decline before the
Turning Point, when nothing will ever be the same again. Beaten into
shape by a ninja babe and a huge telepathic man's best friend, Jack
hurtles across the ocean to save the future from the present and to
solve the mystery of his purpose. Exactly who, or what, is Firestorm,
and what does it have to do with Jack? And what comes next when
everything you have ever known turns out to be wrong?