Unmanned underwater vehicles (UUV) are any vehicles that are able to operate underwater without a human

Human

Humans are the only living species in the Homo genus...

 occupant. These vehicles may be divided into two categories, Remotely operated underwater vehicles (ROVs), which are controlled by a remote human operator, and Autonomous underwater vehicle

Autonomous Underwater Vehicle

An autonomous underwater vehicle is a robot which travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles...

s (AUVs), which operate independently of direct human input. The latter category would constitute a kind of robot

Robot

A robot is a mechanical or virtual intelligent agent that can perform tasks automatically or with guidance, typically by remote control. In practice a robot is usually an electro-mechanical machine that is guided by computer and electronic programming. Robots can be autonomous, semi-autonomous or...

.