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One technique I have used in the case of current is to take a float ball line down with the lead (dive bomb) diver, and have all the other divers essentially dive bomb but keep in sight of the down line (the same current that affected the lead diver is affecting them, so it isn't all that hard to do). That way, all of the divers end up in the same area (even if they are all off the wreck). The boat remains unattached, and simply keeps the float ball in sight throughout the dive, AND the ascent (which is a drifting ascent). That has worked for me. But, other divers may have found better techniques.
Yes, and Yes! Thanks for the comment.Off the face of it I can see some minor risk of self-entanglement, but practice should clear most of it.
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 always thought "negative entry" was the way dumpsterdiver used it. Usual entry is inflated BC, do whatever you need to do on the surface, then deflate and drop. "Negative entry" is deflated from splash. I did not think "negative entry" referenced adding more weight than normal.
Although I do think operators tend to overweight divers if its a drift dive -- that is if you let them decide your weight. Last drift dive I did I asked for 12 lbs (with a 3 mm shorty), the operator insisted I use 14 lbs because it was a drift dive. As I wasnt completely sure of my weighting (hadnt been in tropical waters in a while), I gave in and accepted the extra weight. In restrospect I was probably overweighted -- hell 12 lbs is probably a bit heavy,
But, I've never heard of someone purposefullly overweighing themselves by 10 lbs!!! That's alot of weight and clearly overkill.
I agree that kicking down is a better option.
I've seen a fair number of injuries with backward rolls. Usually a newer diver bangs their head on a valve or occasionally on the hull depending on sea conditions. There's a reason that a good DM will watch you go in and watch for you to surface unless the situation requires a (briefed) departure from standard.Why waste all that momentum that you have jumping off a boat to come back to the surface? Why do you need to be overweighted to achieve a negative entry? You just jump or roll off, exhale and kick with your head pointed down. I'm not coming back to the surface to signal a crew member that I'm "OK" - of course I'm OK, I haven't even done anything yet.