What weapon does the base in Lego's "Aquabase Invasion" use to defend itself?

The base in LEGO’s “Aquabase Invasion” uses harpoon cannons to defend itself. The weaponry is part of LEGO set 7775, an Aqua Raiders underwater base released in 2007.

The base features two front-mounted harpoon cannons, each built to resemble a Gatling gun. They are mounted on ball joints, allowing them to swivel, and each cannon holds six spear-like harpoons. A separate spring-loaded gun sits on top of the base, so the harpoon cannons are not the set’s only defensive feature.

The set belongs to LEGO’s Aqua Raiders theme, which revived ideas from the earlier Aquazone underwater sets. Its story centers on divers protecting the base and its treasures from a giant squid and other underwater dangers. A common mix-up is confusing the base’s harpoon cannons with the large harpoon gun included in the separate Tiger Shark Attack set.