In many basic Open Water scuba courses, divers are taught vertical body position for ascents and descents. While there are some benefits to this technique, a horizontal body position is safer, more effective, and much easier to execute.
The prone body position, preferred while diving, is also the preferred body position for ascents and descents.
Below is the prone/horizontal/skydiver body position:
Below is the vertical body position that most divers use for ascents and descents:
The horizontal diver position provides a significant drag in the vertical water column. The wider profile helps control buoyancy as well as slows the rates of ascents and descents.
The vertical diver position provides less drag in the water column. As the result, it takes more effort to maintain position and rates of ascents and descents are faster.
The above illustrations are from the side profile. However, viewed from the top, the profile differences between the horizontal and vertical positions is even more dramatic.
For descents, it’s usually easiest to descend the first 2′-3′ in vertical position since it’s the most steamlined. Once the surface tension is broken and compression starts, then the diver switches to a horizontal position to help control the descent rate and allow for maximum mobility.
Because of the benefits of drag on the horizontal driver, this position offers the most stable platform. This stability is particularly useful if the diver becomes task loaded or needs to resolve an issue during descents, ascents, or safety stop.
Most diving issues occur during descents or ascents. Even with the appropriate equipment and bubble checks, the descent is when your gear is first being tested. In our local waters, descents are also a common time for buddy separation. During ascents, issues include OOAs and gas switching mishaps. In these situations, the diver needs to be able to maintain neutral buoyancy while resolving the issue. The horizontal position makes this much easier.
Field of View
During the descent, a horizontal position provides optimal field of view. Both positions allow for looking forward at your teammates, but the horizontal position provides a great birds eye view of the bottom.
The horizontal position does limit your ability to look above you. But teams should descend and ascend together, at the same rate.
During ascents, in areas where a total horizontal position ascent may be dangerous (e.g. ships overhead), then switching to a more vertical body position in the last few feet may prove helpful. However, the best ascent strategy is to ascend in teams and have your teammates watch overhead and behind you.
In addition to vertical drag benefits of the horizontal body position, the prone position allows quick access to all kicks. These could include the small kicks for positioning the diver with the team and the environment. It also includes large kicks to quickly reach a teammate if there is an issue.
A diver in the vertical position has less horizontal mobility. Kenn (Gombessa on ScubaBoard) notes the vertical position also reduces vertical mobility. In the horizontal position, tilting up or down offers quick adjustments. In the vertical position, moving up is easy but moving down requires a full inversion.
The biggest issue with the vertical position is the use of fins to maintain position in the water column. Not only does this require work (consuming more gas), kicking to control buoyancy is not a stable position. In order to maintain buoyancy or control, the vertical diver must manage the BC and kick a consistent cycle. Alternately, the horizontal diver simply uses the BC or breath control.
In addition, a diver kicking in vertical position has an impact on the environment. On descents, silt and sand can be kicked up by a vertical diver’s fin movement. It’s not uncommon to see great viz, until divers descend onto the ocean floor. Fortunately, this can be eliminated if divers descend in horizontal position with their fins parallel to the ocean floor.
Rate of Descent and Ascent
While there’s generally prescribed rates of descent (slow enough to allow sufficient equalization) and ascent (30 ft/min), the overall goal is control.
Upon reading this article, Ben (ben_ca on ScubaBoard) made a good comment about the need to arrest your descent/ascent with relative ease. He recommends a range for beginning divers of 4-5 ft and advance divers of 1-2 ft.
Not only is this control helpful in managing ascent/descent related issues such as blocks, but it is useful in keeping buddy teams together and being available to help if required.
A good way to practice is to make predetermined stops on descents and ascents. For example, instead of descending immediately to the bottom, agree with your buddies that everyone will stop at 10′ and 20′. On ascents, safety stops can be done at 30′ for 1 minute, 20′ for 1 minute, and 10′ for 1 minute.
How to Descend
Below is high level descent strategy, the diver will need to adjust to local conditions.
- Signal descent, get confirmation
- Dump gas
- Confirm legs are not kicking
- Transition to horizontal position
- Look at buddy
- Look at environment
- Add gas to control descent speed
- Repeat 7-10 until hovering comfortably off the bottom
How to Ascend
Below is high level ascent strategy, the diver will need to adjust to local conditions.
- Start neutrally buoyant in horizontal trim
- Signal ascent, get confirmation
- Inhale to start ascent
- Look at buddy
- Look at environment
- Dump gas to control ascent speed
- Repeat 4-6 until the safety stop
- Conduct the appropriate safety stop(s)
- After safety stop(s), continue to slowly ascend until the surface