Overlooking Boston Harbor, the New England Aquarium celebrates all things from the sea. From the first-floor pools, where three species of penguins live, ramps spiral upward, encasing the central Giant Ocean Tank, a four-story fishbowl-on-steroids that holds 200,000 gallons of seawater. Through 52 large windows you get a diver’s-eye view of barracudas, sea turtles, sharks, moray eels and hundreds of little fishies that live in the fiberglass and resin “coral reef “ at the tank’s center. Around the outer edges are exhibits on wondrous creatures: sea dragons (a sea horse relative), multi-colored lobsters, fish that glow in the dark and puzzle-solving octopi. Perennial favorites, and the first thing you should check the times for as you enter, are the daily training sessions with harbor seals and half-ton California sea lions. The New England Aquarium operates the whale watch boat Voyager III, which makes regular excursions, by reservation, to Stellwagen Bank to see whales, dolphins and other marine life in the wild.