By MBTA / Subway

From the Green and Orange Lines

From the Green Line, connect to the Blue Line at Government Center.
From the Orange Line connect to the Blue Line at State Street.
Take the Blue Line toward the Airport and get out at the Aquarium stop.

Nice weather? Skip the Blue line and walk down from Government Center
Just go straight out of the station, cross Congress street, straight down past Faneuil Hall and Quincy Market.
At the far end of Quincy Market, cross to the other side of the Rose Kennedy Greenway, then turn right.
The Aquarium is to your left, on its own wharf parallel to the Marriott Hotel.

From the Red Line

From Alewife, connect with the Green Line at Park St., then connect with the Blue Line at Government Center and proceed as above.
From Braintree, connect with the Orange Line at Downtown Crossing, then connect with the Blue Line at State Street and proceed as above. Or skip the Blue Line and walk down from Government Center (see Green Line/Orange Line above).

From North Station

When you arrive at North Station, follow the signs up to the Green Line station.
Take the Green Line inbound two stops to Government Center, then change to the Blue Line and go two stops to Aquarium.
Or skip the Blue Line and walk down from Government Center (see Green Line/Orange Line above).

MBTA map