The Giant Ocean Tank, the penguin colony and the touch tank, plus behind-the-scenes tours and school-vacation programming for older kids.
Details change often — check with the program.
New England Aquarium is listed in the GOkidOZ guide to museum classes and family tours across Massachusetts. Class schedules, free hours and vacation-week programmes change term by term — check the official site above for current listings, and see what else is on during winter break.