When do you Consider Surface Assistant.

[Remy B.]

I'm curios if the Wreck professionals consider a Surface Assistant or they relay completely on them self in the most demanding dives. it is well understands that you need to be self sufficient and carry all your gear with you, but for big dives ( OC ) I guess ( and maybe wrong ) you can carry so much bottles to a point to be unpractical and I believe dangerous to some point.

Of course it is of each individual risk assessment under which risk they determine their dives and are willing to go for that deep and long dive.

What I mean with a Surface Assistant or how I pictured ( never met one nor I know the complete spectrum of their duties ), is a Diver that stays in surface monitors the dive time and have waiting for you at 9m or 6m that extra backup O2 Deco bottle, in that will meet you at the 21m stop to see if everything is alright or assist you if needed, and/or wait for that SMB to come up with a note saying you have problems below, and he will dive down with that extra gas/gear you need to safely return to surface.

 

[DevonDiver]

Higher level dives often entail the use of surface support.. and support divers.

Depending on the dive, there might be 'on-call' standby divers on the surface, or support divers en-situ at varied depths. The logistical complexity of this grows exponentially as you seek to employ support divers at where increasing depths.

There may even be divers on standby to support IWR. Again, complex logistical demands.

Even on 'routine' technical dives, prudent teams might ensure some capacity for support.

In the most simplistic ways, this could include staggering dive teams so that descending teams are in a position to assist ascending teams. It might include staged deco cylinders or even surface supplied deco hoses on a trapeze.

None of this excludes that the primary divers should be self-sufficient throughout the dive.

 

[Remy B.]

But at what depth and bottom time you begin to consider Surface support, I'm thinking more that the amount of bottles is what limits the dive, there is where I guess you leave those backup Deco bottles hanging at 9m or 6m and have the support diver meet you at 21m to hand you over the 50% O2 in case your or one of the team have a problem.

As a example, 70m for 35min BT, with GF 40/70 , 50% and 80% and Trimix as BTG and 21/25 as travel Gas, puts on you a lot of bottles at max, so if you lose one Deco gas you are already screwed, because you can't complete the dive without omitting Deco time, in that case I believe is the correct time to have a support diver if one is willing to take the risk of not carrying all the necessary backup gas volume, or am I missing something that shall be considered as another option that is not a re-breather ?

 

[DevonDiver]

People requiring that much gas tend to be diving CCR. Ultra-deep OC dives tend to be rare nowadays.

A 70m, 35m dive doesn't require a 'lot' of gas... and losing a deco cylinder is bad news for anything other than very light deco. There's a lot of contingencies for that; last on the list are external gas supplies (external from the diving team).

Support divers are needed, and utilised, on the basis of risk management for a given dive/s. There's a lot more to it than just acting as pack animals to hump cylinders to depth.

 

[dumpsterDiver]

When I do a planned deco dive with a drifting deco, I like to have my teenage son on board to use his keen eyes to help spot the smb and also to snorkel down 20 or 25 feet to check on the deco diver status. He's never had to bring me an extra tank. But I think it enhances thesafety of the dive.

 

[Wookie]

I think the amount of surface support depends on the depth, complexity, composition of the dive team, a million factors that make up the dive. As DD said above, he likes his son to be on the boat for any drifting deco dive. I go a little further, that for any dive, I want surface support (I would never leave a boat empty with divers in the water). That may be someone at the quarry heating water to pour in your wetsuit, or even someone at home that will call for rescue if you are overdue from your dive and don't check in. It may be someone humping cylinders (WKPP used a tremendous number of support divers for their exploration dives in the 80s and 90s) or it may be someone who jumps in on a rebreather and dives to 450 feet for a world record setting free dive, in case something goes wrong. In that case, the safety diver watches a freediver die, there isn't much they can do if something goes wrong. Anyway, you can take a class in all of this, or you can hang out and schlep tanks for a team that is doing it, and actually learn the ropes.

Short answer is "it depends".

 

[tbone1004]

what Andy said is basically accurate, but it's not depth/bottom time for me, it's decompression time and practicality. Sometimes you can't carry enough deco gas with you and in the open water, you can't stage them like you would in a cave. At that point, you are going to want someone to hop in when you get to your deco stops and swap bottles with you to get rid of the empty ones if you had to bailout from CCR *I don't know anyone doing these kinds of dives on OC anymore btw*, and give you new bottles to finish your decompression etc etc. These are usually triggered by shooting an SMB with a note on it that says "I need this" etc.

This is real expedition grade diving btw, and not something that you see done all that often. An AL80 gives you a LOT of decompression time when diving in OW since you don't have the travel time like you do in a cave so the deco obligations don't build up nearly as badly

 

[Remy B.]

Decompression model: ZHL16-B + GF

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 40/70

Dec to=== 70m === (3) Trimix 16/50
Level === 70m === 31:07 (35) Trimix 16/50 1.27 ppO2, 24m ead, 30m end
Asc to=== 57m === (36) Trimix 16/50 -8m/min ascent.
Asc to=== 42m === (38) Triox 21/25 -8m/min ascent.
Stop at=== 42m === 0:30 (39) Triox 21/25 1.09 ppO2, 26m ead, 29m end
Stop at=== 36m === 2:00 (41) Triox 21/25 0.96 ppO2, 21m ead, 24m end
Stop at=== 33m === 1:00 (42) Triox 21/25 0.90 ppO2, 19m ead, 22m end
Stop at=== 30m === 2:00 (44) Triox 21/25 0.84 ppO2, 17m ead, 20m end
Stop at=== 27m === 3:00 (47) Triox 21/25 0.77 ppO2, 15m ead, 18m end
Stop at=== 24m === 5:00 (52) Triox 21/25 0.71 ppO2, 13m ead, 15m end
Stop at=== 21m === 4:00 (56) Nitrox 50 1.54 ppO2, 10m ead
Stop at=== 18m === 4:00 (60) Nitrox 50 1.39 ppO2, 8m ead
Stop at=== 15m === 6:00 (66) Nitrox 50 1.24 ppO2, 6m ead
Stop at=== 12m === 10:00 (76) Nitrox 50 1.10 ppO2, 4m ead
Stop at=== 9m === 12:00 (88) Nitrox 80 1.51 ppO2, 0m ead
Stop at=== 6m === 60:00 (148) Nitrox 80 1.28 ppO2, 0m ead
Surface=== (149) Nitrox 80 -6m/min ascent.

OTU's this dive: 204
CNS Total: 78.6%

5473.9 ltr Trimix 16/50===== 12L 300bar x2 or 11L 200Bar x3
1146.6 ltr Triox 21/25===== 12L 300 Bar or 7L 300bar or 11L 200Bar all X1
1020.3 ltr Nitrox 50===== 11L 200Bar x1
2020.7 ltr Nitrox 80===== 11L 200Bar x1
9661.6 ltr TOTAL

It is not a "lot" of gas, my mistake of mental calculation, I ran this now in the PC, you can complete a dive losing either Deco gas, in a unlikely event.

When will you guys consider a Surface support Diver when more than 6 tanks are required or you go for 8 tanks before considering it ?

 

[Wookie]

30 minute 210 foot dive? I wouldn't carry more than twin 120's with 2 80's, one of 32 and one of 80. I would have my support diver meet me at 33 meters on 32 and ask if I'm OK.

 

[tbone1004]

I wouldn't "require" surface support for that dive and certainly not any support divers. Surface support is always nice to have so you take it when you can get it, and the boat crew counts as that.

For that dive, I wouldn't personally use a 21/25 bottle or any deep trimix bottle. I would either swap it and the 50/50 bottle for a 30/30 bottle, or stay on backgas until I got to the 50/50 bottle. If you stay on the deep mix, it only increases your consumption to ~250cf/7000l for easy math, which isn't all that much. That is a pair of LP95's for those of us in the states.
Doing that dive, you plan with the boat crew that you'll shoot a DSMB when you get to the deep deco mix to signal you are OK or if you need help. If you need help, that's obviously preplanned for how the boat is going to react to that kind of situation if your buddy is unable to help you resolve.

I would need at least double that decompression before I planned for a support diver.