Link below about 721 Squadron Royal Danish Airforce and their CL604 MPA. Includes interior photos and and one photo showing drop capability from the rear cargo door.
721 Squadron ? Danish transport squadron | FLYMAG
From the article;
The search is done typically by a rapid descent to a lower altitude, typically 500-800 feet at a speed of about 200 knots, in the area where the missing person or ship is believed to be.
It then searches the area both visually and using the FLIR camera, flying a search pattern which is slowly expanded in the direction the missing persons or ship would have drifted with the wind and currents known to be in the area. This is a situation where the Challengers five man crew comes into good use. Everybody keeps a lookout for the missing persons and if needed, the flight engineer can drop a life raft and/or a marker in the vicinity of those in need.
When the missing persons are found, the aircraft descends to about 100 feet and make a fly-by to confirm that it is in fact the people they were looking for and to assess their situation. At the same time, the aircraft position is plotted and sent to the relevant authorities, who then dispatch either a rescue helicopter or rescue boat.