I'm currently a biology student, though not marine biology. Tell him not to
underestimate the amount of math involved in biology. I did. Algebra, physics,
and chemistry are core studies. If your school has a college prepatory program,
that would help. If he works hard at these subjects, he'll be better prepared
for whatever program he decides. As for graduate school, it's too early to
worry about that unless you plan to pay for it. In that case, definetly plan
for it.
Don't worry about which schools, if your son expresses an interest, they will
find you. I received mail every day for a year from the four winds <g>.