Autonomous underwater vehicles (AUVs)—which operate without a tether or human supervision—represent an emerging technology that can be used to solve many scientific problems in the deep ocean, the last unexplored frontier on Earth. AUVs are well suited to “lawn‐mower” style geophysical surveys for mapping bathymetry, magnetic field, or water column properties. They are fast and efficient synoptic mappers and are inexpensive to operate.Manned submersibles and remotely operated vehicles (ROVs) allow intensive study of an area, but can remain at a site for only a few hours, days, or weeks. AUVs can remain in an area gathering data in between submersible and ROV visits to provide information on temporal variations and can respond rapidly to events such as volcanic eruptions when large oceanographic vessels and equipment cannot be mobilized quickly.