Device for collecting and temporarily storing fluids from an underwater source

device (10) for collecting and temporarily storing fluids (16) escaping from an underwater source (12, 64) and having lower density than surrounding water, said device comprising:

• a collector (18) for being placed over the underwater source (12, 64) for collecting the fluids (16) escaping from the underwater source (12, 64);
• a riser tube (20) having a lower end (24) in communication with the collector (18) for transferring the collected fluids together towards the surface;
• a buoyant buffer reservoir (22) configured for being maintained submerged at a predetermined depth under the surface (26), the buffer reservoir (22) comprising a chamber (30) with an open bottom for storage of the fluids transferred by said riser tube (20),
• wherein said riser tube (20) has flow restrictors comprising choke disks (58, 58′) arranged in its interior for restricting the flow of said fluids, said flow restrictors being arranged at variable or regular intervals all along the length of the riser tube (20) and in that the buffer reservoir (22) has arranged in its chamber (30) a separator vessel (32), into the interior of which said riser tube (20) opens with its upper end (28) for discharging the collected fluids;
• said separator vessel (32) being configured for separating gas from the fluids discharged by the riser tube (20).