Short Answer 
Free diving is limited to approximately 30 meters (98 feet) due to risks like nitrogen narcosis and decompression sickness. With proper training and equipment, scuba divers can safely reach up to 40 meters (130 feet), while professional saturation divers can explore depths around 300 meters (984 feet), and submersibles can go deeper than 10,000 meters (32,800 feet) but are not crewed.
Step 1: Understand the Limits of Free Diving
The maximum depth a human can dive without specialized equipment is approximately 30 meters (98 feet). At this depth, pressure begins to increase significantly, which can lead to dangerous conditions if you dive deeper. Key risks include:
- Nitrogen narcosis – a mental state that can impair judgment.
- Decompression sickness – caused by ascending too quickly.
Step 2: Recognize the Role of Training and Equipment
With specialized training and equipment, such as scuba tanks, divers can safely explore much greater depths. For recreational scuba diving, the safe limit is typically around 40 meters (130 feet). The right equipment helps mitigate risks associated with increased pressure, making extended dives feasible.
- Scuba diving gear assists in managing air supply.
- Saturation diving systems enable divers to live at the pressure of their dive site, greatly reducing risks.
Step 3: Explore Professional Deep-Sea Diving Techniques
Professional divers, known as saturation divers, can dive to significant depths, often reaching around 300 meters (984 feet) or more. They operate in pressurized environments to prevent decompression sickness. In extreme cases, submersibles can explore depths exceeding 10,000 meters (32,800 feet), but these are remotely operated and not crewed by humans.
- Only highly trained professionals should attempt extreme diving.
- Extreme depths pose serious risks and require extensive preparation and support.