Abstract
In aquaculture，the net is fixed underwater for a long term. Periphytons are easy to attach to the
net，therefore it is necessary to clean the net regularly. In addition，the net may be broken by the rapid
current or marine animals，it is necessary to repair the net for prevent fishes from escaping to outside of
the net. But huge labor is demanded to clean or repair after lifting up the net. When divers work
underwater，the work is often difficult under the influence that high water pressure and low water
temperature. Therefore，underwater robot is useful to work underwater instead of divers under the
severe situation. As the pre-stage，this paper reports on the underwater mobile mechanism for the robot
of ROV （Remotely Operated Vehicle）type to use at the net.
