Final answer:
Dives below 300 fsw typically involve technical diving, which requires specialized training and equipment due to the increased risks at such depths, especially decompression sickness which can occur upon rapid ascent.
Step-by-step explanation:
The dives below 300 feet of seawater (fsw) usually involve technical diving. Technical diving is a form of scuba diving that exceeds the conventional depth or immersion time limits, or involves penetration into environments beyond natural light zones. This type of diving often requires additional training, equipment, and safety procedures, such as the use of specialized gas mixtures like trimix or heliox to counter the effects of narcosis and oxygen toxicity, which become significant factors at such depths. Divers must be aware of the risks, including decompression sickness (DCS), which is connected with the reduction of barometric pressure as one ascends to the surface. Adequate decompression stops and controlled ascent rates help prevent DCS, and hyperbaric oxygen therapy may be needed if it occurs.