Abstract: A process of pressurization, of supply for effecting a dive for underwater intervention with a breathing mixture with hydrogen, and of decompression of a person making the dive, wherein the person is pressurized to an absolute pressure P.sub.1 of at least 0.45 MPa with a first type of breathing mixtures not containing hydrogen. The person is supplied at least from this pressure P.sub.1 with a second type of breathing mixtures at pressure P as a function of the depth of dive p to which said person is lowered, which second breathing mixture is of hydreliox type containing hydrogen at a minimum partial pressure of 0.33 MPa, oxygen at less than 4% by volume, helium with a partial pressure of more than 0.1 MPa and other gases such a nitrogen with a total partial pressure of less than 0.09 MPa. Supplying this second type of hydrogenated breathing mixtures in accordance with a composition which would locate the dive in one of the zones of the high pressure nervous syndrome or of narcosis is avoided.

Abstract: Rapidly connectable and disconnectable pipe union, comprising a bush on which are fixed one or more pipes provided with a notched flange. It comprises, in addition, a union body on which are fixed one or more pipes. This body comprises an outer threading on which is screwed a nut provided with a toothed rim and a sliding sleeve, connected to the nut by a ring. This nut comprises a toothed rib which meshes behind the notched flange. One application of the present invention is the connection of underwater pipes with one another or onto underwater apparatus by divers or by remotely controlled devices.

Abstract: This invention relates to a union for assembling a smooth pipe end to a bush, composed of two half-unions fitted in each other and assembled by a nut fast with a toothed ring. Each half union comprises a jaw which cooperates with a sliding ring, which ring is displaced by means of a nut fast with a toothed gear. Said jaws comprise on their inner periphery truncated surfaces which cooperate with truncated surfaces carried by said sliding rings to disconnect the half-unions by manoeuvring said lock nuts.

Abstract: This invention relates to a self-propelled machine piloted by operators and working on the sea-bed, such machine comprising on the one hand a self-propelled chassis, comprising an electrically powered hydraulic pumping system driven by a submersible motor fed through a cable connecting the chassis to the surface and, on the other hand, a submarine which fixes itself on a platform connected to the self-propelled chassis, and in which submarine the operators are installed. The platform comprises ramps for precentering and centering the submarine. The submarine is fixed temporarily on the platform by electromagnets, and induction coils enable orders to be transmitted between the submarine and the self-propelled chassis.