Dive Profile
A dive profile is a graphical representation of a scuba diver’s journey beneath the surface, displaying two essential aspects: depth and time. By charting these elements, the dive profile can help determine a diver’s decompression obligation, ensuring a safe and enjoyable diving experience. The primary purpose of a dive profile is to help divers avoid decompression sickness (DCS), also known as “the bends,” by managing their time and depth underwater and scheduling appropriate decompression stops during their ascent.
I. Dive Profiles and Decompression Theory
- Decompression theory
Decompression theory is based on the understanding that the human body absorbs and releases inert gases like nitrogen at varying rates, depending on factors such as depth, time, and the gas mix being breathed. When a diver descends, the pressure surrounding them increases, causing inert gases to dissolve into the body tissues. As they ascend, the pressure decreases, and these gases are released back into the bloodstream. If the ascent is too rapid or the diver has accumulated a significant amount of dissolved gases, bubbles may form in the tissues and bloodstream, potentially causing serious injury or even death. This is known as decompression sickness.
- Importance of dive profiles
Dive profiles are essential for helping divers manage their exposure to inert gases during a dive, minimizing the risk of DCS. By following a carefully planned dive profile, a diver can ensure that their ascent rate, time spent at depth, and decompression stops are optimized to allow the safe release of inert gases from their body.
II. Elements of a Dive Profile
- Depth
Depth is the vertical distance between the diver and the surface, measured in feet or meters. The deeper a diver goes, the greater the pressure they experience, and the more inert gases are absorbed into their body. The dive profile displays depth on the vertical axis, with the surface at the top and the deepest point of the dive at the bottom.
- Time
Time is the duration of the dive, measured in minutes. The longer a diver spends at a given depth, the more inert gases are absorbed. The dive profile displays time on the horizontal axis, with the beginning of the dive on the left and the end on the right.
- Dive segments
A dive profile consists of several segments, including the descent, bottom time, ascent, and decompression stops. Each of these segments has a specific purpose and contributes to the diver’s overall decompression obligation.
a. Descent
The descent segment represents the diver’s journey from the surface to their maximum depth. During descent, the diver should monitor their depth and equalize their ears and mask to accommodate the increasing pressure.
b. Bottom time
Bottom time refers to the time spent at the maximum depth of the dive. This period is when the diver explores the underwater environment, conducts research, or performs other tasks. The longer the bottom time, the more dissolved gases accumulate in the body, increasing the decompression obligation.
c. Ascent
The ascent segment represents the diver’s return to the surface. Ascent should be slow and controlled to allow the dissolved gases to be released safely. The recommended ascent rate varies depending on the depth and the diver’s decompression obligation but is typically between 30 and 60 feet (9-18 meters) per minute.
d. Decompression stops
Decompression stops are periods of rest at specific depths during the ascent. They allow the diver to off-gas the accumulated inert gases at a safe rate. The number, duration, and depth of decompression stops depend on the diver’s decompression obligation, which is determined by factors such as depth, time, and breathing gas.
III. Dive Computers and Dive Profile Planning
Dive computers are essential tools
for divers, as they automatically record and display real-time dive profile information, including depth, time, ascent rate, and decompression stop requirements. By continuously monitoring the diver’s exposure to inert gases, dive computers can calculate a safe ascent profile and alert the diver if they exceed their decompression limits. Most modern dive computers also include features such as audible and visual alarms, gas switching capabilities for enriched air and technical diving, and the ability to download dive data for post-dive analysis.
- Dive profile planning
Before embarking on a dive, divers should create a dive plan that outlines their intended dive profile. This plan should include information such as the maximum depth, bottom time, breathing gas, and decompression stops. Dive planning can be done manually using dive tables or with the assistance of dive planning software. When creating a dive plan, divers should consider factors such as their personal level of experience, fitness, and the specific conditions of the dive site, such as water temperature, current, and visibility.
IV. Advanced Dive Profiles
- Multi-level diving
Multi-level diving is a technique that involves diving to several different depths during a single dive. This approach allows divers to explore more of the underwater environment and maximize their bottom time while still managing their decompression obligation. By ascending to shallower depths periodically throughout the dive, divers can off-gas accumulated inert gases at a faster rate, reducing their decompression time. Dive computers and multi-level dive planning software make it easier for divers to plan and execute multi-level dives safely.
Technical diving encompasses advanced diving activities that involve specialized equipment, procedures, and training, such as deep diving, cave diving, and wreck diving. Technical divers often use advanced dive profiles that require decompression stops, gas switches, and extended bottom times. These profiles typically involve the use of multiple breathing gas mixes, including enriched air nitrox and trimix, to optimize decompression and reduce the risk of DCS. Technical dive planning and execution require a thorough understanding of decompression theory, advanced dive profiles, and the use of specialized equipment and techniques.
V. Safety Considerations
- Dive profile adherence
It is crucial for divers to adhere to their planned dive profile and follow the recommendations of their dive computer or tables to minimize the risk of decompression sickness. Divers should also monitor their ascent rate closely and ensure they complete all required decompression stops.
- Buddy system
The buddy system is an essential safety practice in scuba diving, as it ensures that divers have a partner to assist in case of an emergency. Buddies should agree on their dive profile and decompression plan before entering the water and communicate regularly throughout the dive to ensure they stay within their limits.
- Emergency procedures
Divers should be prepared for potential emergencies by carrying appropriate safety equipment, such as a surface marker buoy (SMB), whistle, and dive knife. Additionally, divers should be trained in first aid and emergency procedures, such as how to recognize and treat decompression sickness and how to perform a controlled emergency swimming ascent (CESA) if needed.
In conclusion, a dive profile is an indispensable tool for divers to manage their decompression obligation and minimize the risk of decompression sickness. By understanding the principles of decompression theory, utilizing dive computers and planning tools, and adhering to safety guidelines, divers can enjoy the underwater world while ensuring their safety and well-being.
