Although boats, jet skis, and aircraft carriers provide effective means of exploring the oceans, few of them are able to navigate past the inflatable toys of the neighbor's backyard pool. Embrace the aquatic agility of the human body with today's Groupon: for $15, you get a lap-swim and tot-pool punch card (up to a $30 value), valid for five visits to the Marinwood Pool, located in San Rafael. Click here for a schedule of open-swim times.

Surrounded by Marinwood's lush grounds and playgrounds, Marinwood Pool is a communal summer oasis for swimmers of all ages. During each recreational pool session, aquanauts can take laps in the 25-yard-long outdoor pool or slither down the double-flume waterslide. Children under 7 splash each other—despite the clear "No Foalplay" signs—in the enclosed, shaded tot pool. Several poolside events also run throughout the summer, including Sunday fun days that treat swimmers to a family-friendly DJ and bounce house.

Beyond the shores of its community pool, Marinwood Community Services District maintains an uncharted paradise of parks and recreational activities. Wile away the afternoon at Marinwood's multiple tennis courts, playgrounds, and picnic areas, or hit the hiking trails to retrace the steps of Lewis and Clark's infamous gaffe, where they mistook the pool for the Pacific Ocean.