Mermaids and pirates, island girls and sailors welcomed some 750 guests to “Deep Treasures,” the 15th Annual Richmond Heart Gala April 28 at the Science Museum of Virginia. Mosaic Catering hired extras to set the scene, staging an underwater fantasy complete with faux rainstorm (at right) and flying fish. Scuba-divers poured wine.  And Richmonders checked out each other’s black-tie finery and bid high on auction items that included a Jaguar and a trip to Dominica.