Abstract: A system for welding the ends of submerged pipes in a gaseous atmosphere at any depth comprises isolating the ends of the pipes by introducing obturators therein and then introducing the pipe ends into an open topped receptacle which is capped with an underwater personal carrying intervention unit. The closed receptacle is filled with gas and then a sleeve is positioned between the ends of the pipes and welded to the pipes.

Abstract: The ends of submerged pipes are connected using a receiver provided with two apertures through which the pipe ends extend, the receiver being adapted to form a watertight enclosure with an intervention unit and housing means for closing the ends of the pipes comprising two stoppers bearing seal means to be applied against the inner walls of the pipe ends and being maintained spaced apart by a first boom, the receiver including means for supporting a sleeve to be connected to the ends of the pipes and a replacement boom located in the sleeve, the connection being performed by introducing the ends of the pipes to be connected into the receiver through the apertures, at least one of the pipe ends being introduced by movement of the receiver relative thereto, closing the ends of the pipes with the stoppers, causing an intervention unit to descend on to the receiver, providing a watertight enclosure therewith, removing the water from the enclosure and placing it under atmospheric pressure, placing the receiver und

Abstract: To enable the release and consequent recovery of a support float which supports a load, e.g. a pipe, as it is lowered to the sea bed, a marker buoy is lowered with the float to be released when the load reaches the sea bed, the marker buoy having an inflated flexible envelope which is trapped in a housing fast with the float and having an opening through which the float can escape only when it has been compressed to a predetermined extent under the effects of a predetermined hydrostatic pressure. The marker buoy is connected to the float by a cable and the float is released from the load either by operations on that cable, or on a release cable connected to the float, on appearance of the marker buoy at the water surface.