What a question!
First, let me say that I live a long ways from the ocean. That doesn't keep me from being involved. Here are a few things we can do...
1) I'm a teacher. That means I get the chance to show children some of the wonders and issues concerning the seas and oceans. Shaping young minds about vital issues is a great opportunity to influence the future.
2) I volunteer with NOAA and the Flower Garden Banks National Marine Sanctuary. We conduct science expeditions, gather data, perform species counts and monitor the GOM.
3) As a sanctuary volunteer, I get the opportunity to give presentations using extremely current data and images from the NMS (much of which I get to collect firsthand). For example, this past weekend we conducted "virtual dives" at the Texas Parks and Wildlife Expo in Austin, Texas. HUGE numbers of kids, but there were lots of adults, too. Most didn't even know there WAS a coral reef environment in the Gulf...now they do. Next month, I'll be presenting workshops at the Conference for the Advancement of Science Teaching in Wichita Falls, Texas. Six thousand science teachers will be there.
4) I also conduct REEF surveys when I can.
5) I stay current about how human activities can impact the ocean environment.
Okay, this is not to thump myself on the chest or pat my own back. But it proves that one doesn't have to be Jaques Costeau to have an impact. If a "flatlander" from the prairie can get involved, then anyone can.
"We love what we understand, and we protect what we love." If we can get more people to love the oceans, then we'll stand a much greater chance of preserving them for the future.