Tonna tankervillii

Tonna tankervillii is a very large sea snail characterized by its impressive shell size, which can reach heights of up to 23 cm and widths of 19 cm. This species is found primarily in Australian waters, extending from the Torres Strait in the north down the east coast, and it is also present on the northeast coast of New Zealand. Divers may encounter this species in a variety of marine environments, including coral reefs and rocky reefs, where it typically resides in shallow waters close to the coast. Its large size makes it relatively easy to identify among other gastropods, though it may be confused with smaller species of tun snails.  Feeding habits of Tonna tankervillii are not detailed in the sources, but as a sea snail, it likely grazes on algae and other organic matter found in its habitat. Breeding behaviors are also not specified, but many gastropods have complex reproductive strategies that may include external fertilization. When divers encounter Tonna tankervillii, they may observe it slowly moving along the substrate, a behavior typical of many bottom-dwelling gastropods.