Taking advantage of state of the art underwater vehicles and current networking capabilities, the visionary double objective of this work is to “open to people connected to the Internet, an access to ocean depths anytime, anywhere.” Today, these people can just perceive the changing surface of the sea from the shores, but ignore almost everything on what is hidden. If they could explore seabed and become knowledgeable, they would get involved in finding alternative solutions for our vital terrestrial problems – pollution, climate changes, destruction of biodiversity and exhaustion of Earth resources. The second objective is to assist professionals of underwater world in performing their tasks by augmenting the perception of the scene and offering automated actions such as wildlife monitoring and counting. The introduction of Mixed Reality and Internet in aquatic activities constitutes a technological breakthrough when compared with the status of existing related technologies. Through Internet, anyone, anywhere, at any moment will be naturally able to dive in real-time using a Remote Operated Vehicle (ROV) in the most remarkable sites around the world. The heart of this work is focused on Mixed Reality. The main challenge is to reach real time display of digital video stream to web users, by mixing 3D entities (objects or pre-processed underwater terrain surfaces), with 2D videos of live images collected in real time by a teleoperated ROV.