As long as he wants if he has enough gas to do the required decompression. But if you are asking what the no-stop time limit is, it doesn't exists since any dive to 100 meters (328 feet) requires mandatory decompression.
Most recreational divers rarely dive below 100 feet. The average depth for a dive is around 60 feet.AdditionThere is a difference between the average deepest depth of of dives in general and the average depth of a single dive. Most dives will have the deepest depth of around 60 feet, but the average depth of that dive will probably be more in the range of 30 feet since divers will start at one depth and usually continue the dive at shallower depths.
The certification levels for PADI (Professional Association of Dive Instructors) are as follows: *Junior Open Water Diver---minimum age of 10 and the diver cannot go below 45 feet *Basic Open Water Certification--minimum age of 12 and the diver can go to the safe distance of 132 feet *Advanced Open Water Certification--minimum age of 15 *Rescue Diver--minimum age of 18 *Divemaster *Scuba Instructor--the diver is licensed to certify other divers. There are also many specialty courses that one can take, such as wreck diving, deep diving, nitrox diving, search and recovery, and underwater photography.
40 feet (12 meters) to 100 feet (30 meters).
Divers have dived over 1,000 feet on scuba (rarely - only four times so far), so that is probably the outer edges of the limit for technical divers.The deepest level you can be 'certified' to dive at is 330 feet/100 meters (TDI Advanced Trimix/IANTD Expedition Trimix). Wrecks like the HMHS Brittanic and the SS Transylvania are dived with some degree of regularity at depths around 450 feet.But there are no scuba police, and many technical divers in fact exceed those depths regularly. The deepest depths to which technical divers are known to dive with any level of regularity are around 550 or so feet (thinking of the Jolanda in the Red Sea at various depths down to and slightly below 550 feet).Dives below 600 feet are extraordinarily rare.
It's not recommended for a sport diver to go below 130 feet due to the partial pressure of oxygen being poisonous when it reaches the equivelant of 100% (5 atmospheres as there is about 20% oxygen in the air). Also the effect of Nitrogen narcosis can make your decision making erratic. It's not an exact science as to what depth an individual may succumb to this but 130 feet is a good guage of where you are relatively safe as long as you are obeying all the rules of training and you and your buddy are not irresponsible. Any deeper and you would need to mix gases and should get more specialised training.
up to 100 feet away
In oregon 200 feet
A diver is underwater in the area. Stay at least 100 ft away.
It depends upon your state law, but 100 feet would be a general answer.
100 feet
Up to 100 meters which is over 300 feet deep.