Hahave are on Te Pito o Te Henua, the street that runs down to the harbour and where most of Hanga Roa's agencies sit. They sell the standard island circuits with local Rapa Nui guides and transport included in every tour, take every form of payment, and advertise a fixed rate card — which on an island where quotes vary a great deal is worth having in writing before you commit.
They are also registered with SERNATUR for buceo en apnea, free-diving, and given that every other dive operation on Rapa Nui has lost its website, they are currently the only underwater operator here you can actually reach.
Two numbers: one for reservations by voice, one for WhatsApp and emergencies around the clock. The WhatsApp buttons all go to the second one.