The Bay turns arctic on Sunday when thousands of pounds of snow flood the giant tank that is the Aquarium of the Bay at Pier 39. Expect to watch sea otters frolicking like they were suddenly back home in northern seas. Even on normal days the Aquarium holds of hundreds of thousands of gallons of sea water. You can walk through 300 feet of underwater tunnels here hosting walls of jellies, leopard sharks, bat rays, giant sea bass and sea otters. $14 admission.