Aqua Samoa, based at Aggie Grey's Lagoon Beach Resort and Spa near Mulifanua Wharf, organizes daily scuba and snorkeling trips.
On the south coast of Upolu, Liquid Motion is at the Sinalei Reef Resort. It offers scuba diving and open-water certification courses.
Many of the reefs off Upolu's north coast have been damaged by hurricanes and local poachers who use dynamite or a type of poison to bring up fish, so the south coast is now favored for its calmer seas and variety of attractions. The reef channels teem with fish, best seen on an incoming tide. Nu'usafe'e Island just off Poutasi is a favorite for its coral heads, wavy coral, and variety of fishlife (including harmless sand sharks). You can hand-feed the tame fish. Five lava chutes penetrate 10-25 meters and open into clear water. If that sounds good, try going down the main lava chute at Lefaga through a strong current as the surf roars overhead, then over the edge of the reef. This is for experienced divers only.
Other good spots are the drop-offs at Nu'utele and Nu'ulua Islands in Aleipata, the western reef areas off Manono, and the edge of the barrier reef, three km offshore from Lalomalava, Savai'i.