ABSTRACT
Deep water trenches in oceans reach maximum depth of nearly 11000 m. The full depth of the ocean has been reached only once in January 1960 by two crew members in deep capability vessel called Trieste. The human being has never again returned to the full depth of the ocean in a manned vehicle. It appears that at the moment there are only four manned vessels capable of reaching 6000 m, and this is about half of the full depth. Hence, the depths greater than 6000 m remain beyond direct access to humans, see Table 1 and Figure 1. Progress in understanding of the role of the oceans in human development is dependent on provision of a variety of manned and unmanned underwater vehicles being available, Fryer (1990). Further effort is needed in order to acquire submersibles with the necessary characteristics.
