We are leaving port at 11.00, force 4 increasing 5 to 6 and pushing us directly along the channel of Mallorca direction Port Andtratx. There is a gale warning over the radio for the area south of Cabrera and we watch in the extremely clear air the huge buildup and the hammerhead of the thunderstorm up to 12 kilometers high and below dark walls of heavy rainfall. Not the place to be right now. Around midday I see a bright red light to starboard and watching closer I see a sailing yacht of about 15 meters with bow very low, sometimes submerged going direction Ibiza. Sails down, engines on and go, a red light is a mayday or SOS how it was called in former times. No answer over the radio, no reaction on the invitation to come over, so I made a mayday relay and called all stations on channel 16, getting immediate answer from Ibiza radio. I pass on my position and the nature of the emergency and they ask us to wait and standby until the helicopter and the SAR boat arrive. The copter arrives from Mallorca after 20 minutes and launches a frogman, one person jumps off the sinking boat, all a bit strange, and the SAR boat from Ibiza arrives a little later. We radio to the coordinator and he thanks us and we are on tour again and arrive in our destination port at 23.00, awaited by the marinero, who shows us our berth alongside the quay.