From the festival website:

VIMS' [Virginia Institute of Marine Science] annual open house is a fun-filled event for the whole family. Join us in Gloucester Point for exhibits, children's activities, seining on the York River, lab tours, seafood cooking demonstrations, mini-lectures, and much more. All activities are free, as is parking. The event proceeds rain or shine.

Also be sure to check out the parade of marine life, which allows visitors to dress up and march as their favorite marine creatures.