Recreational Dive Planner (RDP): Scuba Diving Explained

The Recreational Dive Planner (RDP) is an integral tool for scuba divers, providing a comprehensive guide to safe diving practices. It is a decompression table that allows divers to plan their dives and manage their nitrogen absorption, thus reducing the risk of decompression sickness. The RDP is a product of extensive research and scientific understanding of the human body's response to pressure changes.

Understanding the RDP is essential for every diver, regardless of their level of experience. It is not merely a tool for planning dives but also a means of understanding the limits of the human body under water. This article will delve into the intricacies of the RDP, exploring its history, how it works, and its practical applications in the world of scuba diving.

History of the Recreational Dive Planner

The development of the RDP is a significant milestone in the history of scuba diving. Before its inception, divers relied on rudimentary methods to plan their dives, which often led to accidents and fatalities. The need for a reliable and scientific method to plan dives led to the creation of the RDP.

The RDP was developed by the Professional Association of Diving Instructors (PADI) in collaboration with DSAT (Diving Science and Technology). It was introduced in the late 1980s as a safer and more user-friendly alternative to the existing decompression tables. The RDP has since undergone several revisions to improve its accuracy and usability.

Role of PADI and DSAT

PADI and DSAT played a crucial role in the development of the RDP. PADI, as the world's leading scuba diver training organization, recognized the need for a reliable dive planning tool. DSAT, on the other hand, provided the scientific expertise required to develop such a tool.

DSAT conducted extensive research on the effects of nitrogen absorption and release in the human body during and after dives. This research formed the basis of the RDP. The collaboration between PADI and DSAT resulted in a tool that is now used by millions of divers worldwide.

Understanding the Recreational Dive Planner

The RDP is a decompression table that provides divers with information on the maximum allowable bottom time for a given depth, taking into account the residual nitrogen in the body from previous dives. It is based on the understanding that the deeper a diver goes, the faster their body absorbs nitrogen, and the shorter their bottom time should be.

The RDP is divided into three sections: the Dive Table, the Surface Interval Credit Table, and the Repetitive Dive Timetable. Each section serves a specific purpose in the dive planning process.

The Dive Table

The Dive Table is the primary section of the RDP. It provides information on the maximum allowable bottom time for a given depth. The table is divided into pressure groups, each represented by a letter. The pressure group changes as the depth and bottom time change.

For example, if a diver plans to dive to a depth of 60 feet, they would refer to the Dive Table to find the maximum allowable bottom time for that depth. The corresponding pressure group would then be used in the next stages of the dive planning process.

The Surface Interval Credit Table

The Surface Interval Credit Table is used to determine the residual nitrogen level in the body after a dive. After a dive, the body continues to release the absorbed nitrogen. The time taken for this process is known as the surface interval. The longer the surface interval, the more nitrogen is released from the body.

The Surface Interval Credit Table provides information on the pressure group after a given surface interval. This information is used to adjust the allowable bottom time for subsequent dives.

The Repetitive Dive Timetable

The Repetitive Dive Timetable is used to plan subsequent dives. It takes into account the residual nitrogen in the body from previous dives and adjusts the allowable bottom time accordingly.

For example, if a diver plans to make a second dive to a depth of 60 feet, they would refer to the Repetitive Dive Timetable to find the adjusted bottom time for that depth, taking into account the residual nitrogen from the first dive.

Using the Recreational Dive Planner

Using the RDP involves a series of steps that begin with determining the planned depth and bottom time and end with a safe ascent to the surface. The process requires a thorough understanding of the RDP and careful calculations to ensure a safe dive.

The first step in using the RDP is to refer to the Dive Table to determine the maximum allowable bottom time for the planned depth. The diver then records the pressure group at the end of the dive. After the dive, the diver refers to the Surface Interval Credit Table to determine the new pressure group after the surface interval. This new pressure group is then used in conjunction with the Repetitive Dive Timetable to plan any subsequent dives.

Calculating Bottom Time

Calculating the bottom time is a crucial step in using the RDP. The bottom time is the total time spent underwater from the beginning of descent to the start of the final ascent. It does not include the time spent on the surface or the time taken to ascend to the surface.

The bottom time is determined by referring to the Dive Table. The diver finds the planned depth on the table and reads across to find the maximum allowable bottom time. This time is then adjusted for any residual nitrogen in the body from previous dives by referring to the Repetitive Dive Timetable.

Managing Residual Nitrogen

Managing residual nitrogen is another important aspect of using the RDP. After a dive, the body continues to release the absorbed nitrogen. The time taken for this process is known as the surface interval. The longer the surface interval, the more nitrogen is released from the body.

The diver uses the Surface Interval Credit Table to determine the new pressure group after the surface interval. This new pressure group is then used to adjust the allowable bottom time for subsequent dives by referring to the Repetitive Dive Timetable.

Limitations of the Recreational Dive Planner

While the RDP is a valuable tool for dive planning, it is not without its limitations. It is based on a theoretical model of nitrogen absorption and release in the body, and it does not take into account individual variations in physiology or health conditions that may affect a diver's nitrogen absorption rate.

Furthermore, the RDP does not account for factors such as cold water, strenuous exercise, or diving at altitude, all of which can increase the risk of decompression sickness. Divers must therefore use the RDP in conjunction with good judgment and a thorough understanding of their own physical capabilities and limitations.

Individual Variations in Physiology

Individual variations in physiology can significantly affect a diver's nitrogen absorption rate. Factors such as age, fitness level, body fat percentage, and health conditions can all influence how quickly the body absorbs and releases nitrogen.

The RDP does not take these individual variations into account. It is based on a theoretical model that assumes a standard rate of nitrogen absorption and release. Divers must therefore adjust their dive plans according to their own physical capabilities and limitations.

Environmental Factors

Environmental factors such as water temperature, physical exertion, and diving at altitude can also affect a diver's nitrogen absorption rate. Cold water can increase the rate of nitrogen absorption, while strenuous exercise can increase the body's oxygen consumption, leaving more room for nitrogen to be absorbed.

Diving at altitude can also increase the risk of decompression sickness, as the reduced atmospheric pressure allows nitrogen to be released from the body more quickly. The RDP does not account for these environmental factors, and divers must therefore take them into consideration when planning their dives.

Conclusion

The Recreational Dive Planner is an essential tool for scuba divers, providing a comprehensive guide to safe diving practices. It allows divers to plan their dives and manage their nitrogen absorption, reducing the risk of decompression sickness. However, it is not without its limitations, and divers must use it in conjunction with good judgment and a thorough understanding of their own physical capabilities and limitations.

Understanding the RDP is not merely a matter of learning how to read a table. It requires a deep understanding of the principles of diving physics and physiology, as well as the ability to apply these principles in a practical context. With practice and experience, divers can use the RDP to plan safe and enjoyable dives.