Happy World Oceans Day - sort of.  Today marks the annual observance of the vast water bodies that cover nearly three-quarters of Earth's surface.  It's a time for taking stock.

Oceans regulate our climate (El Nino and La Nina, anyone?) and feed us, among other things. But 90 percent of the big predator fish that once roamed the seas are gone, according to biologists, and 20 percent of the coral reefs are similarly depleted.  Yet less than 2 percent of the oceans are formally protected.

The National Aquarium is going to mark the day by having its CEO, John Racanelli, dive in one or two aquarium exhibits this afternoon with reef conservationalist John Halas, a marine biologist and manager of the Upper Region of the Florida Keys National Marine Sanctuary.

Over the weekend, the aquarium will continue ocean-themed activities from 10 a.m. to 3 p.m., including a scavenger hunt and a chance to swap some plastic grocery bags for a free re-usable tote.  All activities are free with admission, $20.95 for children up to $29.95 for adults.

For other World Oceans Day activities elsewhere, go here.