The rock is a piece of Waitemata Group sandstone exposed in the Waitematā Harbour.[1] The rock is an intertidal reef, exposed during low tide.[2] The surface of Boat Rock is covered in sand and shell deposits.[2]
The island was traditionally referred to by Tāmaki Māori iwi by various names, including Te Nihokiore ("The Rat's Tooth"), Timata, Te-Toka-tu-Moana ("The Rock Standing in Mid-Sea"), Te-Waka-o-Tawaroa and Te Mata-o-Kahu.[3][4] Te Nihokiore is likely a metaphor for how the rocks remain sharp despite being battered by the sea, similar to a rat's tooth.[4] The island is the namesake of the Waitematā Harbour, which literally means "Waters of Te Mata".[5] The name refers to Te Arawa chief Kahumatamomoe, who when visiting the harbour placed a mauri stone (a stone of religious significance) on Boat Rock.[5] The name Waitematā originally only referred to the upper harbour area near Boat Rock.[6] Boat Rock was traditionally used as a rohe marker, designating the boundary of influence between different Tāmaki Māori iwi.[7]
The waters surrounding Boat Rock were a traditional fishery, known by the name Waipokanoa ("The Waters of Foolishness").[7]
In 1873, an iron ship beacon was erected on the island,[8] which was damaged by ships in 1905.[9]
