Keep in mind that the Seenotdienst was a joint sea-air rescue organization, so they had boats and aircraft.
An interesting side note: Luftwaffe Lt. Col. Goltz, who was in charge of the program, was the only German Air Force officer to have command over ships and boats!
Also when war broke out, the Seenotdienst's first rescuees saved, were RAF Wellington crewmembers, about 22 in all.