From the current PADI Divemaster manual:
Stamina Assesment and Development:
There are four exercises that evaluate stamina and water skills, each rated by points. There is no passing score for any single exercise, but a combined score of12 or more is required prior to certification.
1. The candidate must swim 400 meters or 400 yards without stopping using no swimming aids and using any stroke or combination of strokes desired.
2. Using no aids and wearing only a swimsuit, the candidate will stay afloat by treading water, drown proofing, bobbing, floating, etc., for 15 minutes, with hands (not arms) out of the water during the last 2 minutes. A candidate with a physical challenge that makes it difficult/impossible to hold hands out of the water is exempted from that portion of the exercise with no effect on the score.
3. Using a mask, fins, snorkel and swimsuit only (no BCD or flotation aids) and swimming with the face in the water, the candidate must swim nonstop 800 metres/800 yards. The candidate may not use arms to swim, unless the candidate has a physical challenge that limits leg use and arm-swimming as the individual's normal swimming method while diving.
4. Wearing full scuba equipment, the candidate must push or tow an inert diver in full scuba at the surface 100 metres/100 yards nonstop without assistance.