Before revision: These also have been considered since the late 1960's for use in offshore oil exploration and production in extremely deep water, but practical devices have used other technologies from the sea surface, such as moored barges and tension leg platform
After revision: These also have been considered since the late 1960's for use in offshore oil exploration and production in extremely deep water, but practical devices have used other technologies from the sea surface, such as moored barges and tension leg platforms.