Negative Entries - A Bad Idea???

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I recently came across a thread about diving in a particular location with currents where a poster stated:



Personally, I think negative entries are a bad idea, and especially when currents are involved. Using excessive weight for downward directed propulsion is going to be either ineffective, or unsafe if it's big enough to be effective. A negative entry seems to invoke too much risk when there are better ways to deal with diving in currents.

My impulse is to caution divers to think about the consequences of negative entries vs. other methods of getting down quickly. My personal preference is to dive with the ideal amount of weight (the minimum needed to be neutral at about 10 feet with an empty tank), and then kick down for a rapid descent if that is what's desired for the dive plan.

An extra 10 pounds of lead will take you down, but if you parachute drop, that 10 pounds is working against the maximum drag profile of the diver moving through the water. You won't descend nearly as fast as a diver who swims down by kicking with an average of 10 pounds thrust and is exposing a minimum cross-section and minimum drag to the water. This level of thrust is easy to produce with decent dive fins. Even a draggy diver should be able to swim in excess of 90 ft/min and a typical recreational scuba diver should be able to easily exceed 150 ft/min. That seems like a fast enough descent to me.

Also undesirable is that any extra weight carried by a diver to do a negative entry will then require the diver to inflate their BCD once down to achieve neutral buoyancy. The extra BCD inflation will then increase the diver's drag in the water making it harder for them to deal with the currents for the duration of the dive.

A diver who uses ideal weighting and swims down will have less drag and be more effective at dealing with the currents during the course of the dive. This diver is also not exposed to the risks of hitting the water negatively weighted and then potentially having to deal with another diver related problem (tank valve not open, regulator failure, BC or DS not connected, etc...) while sinking out of control.

I put the negative entry in the same category as hyperventilating when freediving. It's an idea that has the illusion of making the dive easier, but it really just adds unnecessary risks without delivering a true positive benefit.

These are my thoughts on negative entry diving and why I think it is a bad idea. Am I missing certain applications that would make the negative entry a good idea? I'd like to hear what others have to say on the subject.
I appreciate this is an old post, but having just written about negative entry diving on my diving blog, I came across this post and wanted to answer this question here too.

The application you are missing is using a negative entry in a strong current, for example when I've dived Elphinstone Reef in the Red Sea a negative entry is a must, otherwise you miss the best dive spot on the dive, which is a plateau at about 30 metres (99 feet) where you hold on to a rock and watch sharks swim past, including hammerheads, thresher sharks and oceanic whitetip sharks.

On Elphinstone you need to enter the water quickly and descend quickly head-first and finning to get to the plateau.

However, the point I would add, is you should only be doing negative entries as an experienced diver and in the scenario I describe above, you need to be an experienced diver in strong currents too. If anyone is interested to learn more, my article is here: What Is A Negative Entry In Diving?

Happy diving!! :)
 
I appreciate this is an old post, but having just written about negative entry diving on my diving blog, I came across this post and wanted to answer this question here too.

The application you are missing is using a negative entry in a strong current, for example when I've dived Elphinstone Reef in the Red Sea a negative entry is a must, otherwise you miss the best dive spot on the dive, which is a plateau at about 30 metres (99 feet) where you hold on to a rock and watch sharks swim past, including hammerheads, thresher sharks and oceanic whitetip sharks.

On Elphinstone you need to enter the water quickly and descend quickly head-first and finning to get to the plateau.

However, the point I would add, is you should only be doing negative entries as an experienced diver and in the scenario I describe above, you need to be an experienced diver in strong currents too. If anyone is interested to learn more, my article is here: What Is A Negative Entry In Diving?

Happy diving!! :)
Totally agree. While it's not for beginners negative entries are a tool in the box. My wife and I have used them in instances where clearing the surface quickly is important. Once on a "hammerhead" dive on Molokai where the the best drop spot was a bit choppy and required the boat to get close to a large outcropping. We exited the boat like lemmings off of a cliff, all negative, and met at 15 feet to allow the boat captain to move out to a better spot.
Another time was diving the Bianca C wreck in Grenada. It's deep, current exposed, and there are no buoys. The captain set us up, we back rolled off and went head down as fast as we could to get onto the wreck. It worked perfectly.
 
Noob here.


We jumped in mostly deflated, and finned hard to slow down to equalize. We were on the bottom in 20 seconds. Didn't trim out till the bottom.


Same technique to go up. Dump wing, fin up.
 
Same technique to go up. Dump wing, fin up.

If you are on the bottom and ready to ascend, hopefully, you are neutrally buoyant. Dumping gas from your wing at that time will make you negatively buoyant.

Being negatively buoyant is not really the best way to make an ascent.

For a normal ascent, you should use your breathing to get yourself started floating up. Take an extra deep breath and pause for a moment with your lungs full. If you are neutrally buoyant, that should get you started up.

Once you are moving up, you wait for the gas in your wing to expand. That will make you start to go up more and more quickly. When you are starting to go up quickly, then you dump some gas from your wing to slow your ascent. At no time should you make yourself negatively buoyant. You are just going for LESS positive.

Ascending that way should be more than adequate to achieve a proper and safe 30 feet (or 10 meters) per minute ascent. No need to fin up while making a normal, safe ascent.

If you must go faster for some reason, then it is the same, with the addition of finning to help you go up.
 
In reality, if you ascend vertically, it is easier to control an ascent by staying just a little negative. You kick gently to move up, pause kicking and see if you are floating, sinking or hanging there.

If you are sinking, kick a little more, if hanging motionless, then a gentle kick gets you moving and if you are floating up, then exhale and dump a tiny bit of air from BC. Maintaining a constant positive buoyancy is certainly doable and is relaxing, but it is harder balancing act when you try to never kick at all.

When I start an ascent, I normally tap the inflator or scooter button and actively start the ascent and get a good 15 or 20 feet off the bottom to get things started. But then, I quickly slow down and do a mix of floating and kicking upward for the ascent.
 
Gotta go fast

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Hot drops can be exciting. However, if you're diving an unbalanced rig, be sure to have redundant buoyancy in case you have an issue with primary buoyancy device. That can be a double bladder BC, a drysuit, a lift bag, or even a safety sausage that you can inflate at depth.
 
Hot drops can be exciting. However, if you're diving an unbalanced rig, be sure to have redundant buoyancy in case you have an issue with primary buoyancy device.
Why would someone be diving an unbalanced rig in the first place? With a balanced single tank rig you can just swim it up as you're never very negative even with a full tank. With a balanced double tank rig you might have to ditch some weight, but will still be able to swim up.
 
Why would someone be diving an unbalanced rig in the first place?
Ever dive a steel twinset? Either back or side mount, they be heavy. I know a number of divers who are negative with even a single steel. It's fine, as long as you plan for caca to appear. Most people plan in panacea mode when they should always plan for when the wheels come off. Over plan and over prepare as if your health depended on it. Obviously, within reason.
 

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