What DHARMA Initiative station was located underwater in Lost?

The DHARMA Initiative station located underwater in Lost was The Looking Glass.

The Looking Glass sat on the seabed roughly 60 feet (18 metres) below the surface and about 600 feet (182 metres) from the beach. Unlike the island’s more familiar stations, it was designed for underwater operation and helped maintain the island’s secrecy.

Its main functions were blocking communications to and from the island and generating a beacon that guided the DHARMA submarine. While DHARMA was active, the station also helped resupply that submarine. The Others believed it had flooded, but Ben knew it remained operational and that personnel still worked there.

A common mix-up is The Pearl, which was an observation station, or The Swan, which housed the button protocol. The Looking Glass is also central to the season-three finale, “Through the Looking Glass,” in which Charlie investigates its communications equipment.