Base fed line and underwater ridges

[Subcooled]

We have a new voluntary underwater search and recovery team. We help the police with time consuming searches that are no longer urgent.

We were practicing at a site recently that had a gently sloping bottom 0->4m that then abruptly deepened. There was a steep slope down to 14m. A parallel search pattern with the rope tender walking along the shore was used. The rope however dragged along the ridge causing major silting (and guess where that silt was then heading to...) and it caught every single stone on the shallower already searched area.

How do you solve these issues? Do you have another diver following the ridge and guiding the rope, or are you using floaty polypropylene line instead of nylon, or what? What has proved to be the best practice

 

[Jim Lapenta]

I'm curious as to who developed the protocol for this method. I understand why you would sometimes want a tender on shore. But when it causes this why are you not using a boat? Or why would you not use a line from shore running out to a float and then down to the divers? I am not a PSD instructor but before I would do any further training scenarios with your team I'd find one and get squared away. Silting is a minor problem, having the line get snagged and entanglement that results in a team member drowning is a big problem.

 

[Subcooled]

I understand why you would sometimes want a tender on shore. But when it causes this why are you not using a boat?

It was the first time we used that site. It was a simple sandpit on land (a popular swimming place for families). Getting a boat there would have been a big hassle. Some lakes and ponds may be pretty inaccessible, too. We can get boats and stuff if needed, but use only what is needed for doing it safely... It is easier to get a boat driver and transport of boat for a real search than for a monthly drill as this is not paid work.

A line tender walking on the shore works wonderfully in the river flowing through the city (a narrow river; high riverbanks/stone walls). It didn't work in this other site. And we started thinking about other options, such as using an underwater line tender too (like when searching under piers), floats, floating rope etc.

Or why would you not use a line from shore running out to a float and then down to the divers?

A float came to our minds, but line communication becomes impossible, and full face masks and phones would be needed. We can't afford those, so either we have working line communication, or we skip the task.

having the line get snagged and entanglement that results in a team member drowning is a big problem.

Oh yes. We don't want that.

 

[Lake Hickory Scuba]

Hey there Subcooled, as a Public Safety Diver Instructor and Under Water Criminal Investigator Instructor, not only as a Dive Shop but also by trade (being in the Public Service as a Law Enforcement Officer, Fire Fighter, & EMT), I constantly run into this very situation. In short, THANK YOU for your service as a volunteer, but I can't stress enough the need for proper training before attempting such diving. Searching for items in a Public Service type scenario is a lot different than your typical search and recovery in a recreational since (we search and don't worry about visibility). I think that it is great that you are tendered during these dives, but if visibility disturbance is a concern that you have, then you should really ask yourself, are you properly qualified to do such diving. I notice in your profile you are CMAS trained and certified (great accomplishment, considering I am a CMAS Course Director and understand how hard of a course it is to become certified in CMAS).

Now with that rant over with, I would possibly try a JACK STAY search pattern, and set it up using snorkelers or 2 extra divers, if a boat is unusable in that situation. The JACK STAY, will be the most practical for decompression purposes (doing deep part first), and is a great technique for searching an area methodically, making sure not to miss anything. The surface divers or snorkelers can also be used as tenders.


Another great technique is a half moon circle search. Similar to to a full circle search but you would stop the diver after the 180 degree turn.


Setting up both of these search patterns are pretty simple and materials to do so are not too bad expensive. If you have any further questions please email me, lakehickoryscuba@gmail.com, or shoot me a pm. THANK YOU again for volunteering to help your local Public Service Agencies, but please get properly trained to do so, for your safety and others. Good luck and God Bless.

 

[Subcooled]

Thank you. It's nice that our effort is appreciated. Our team is used to low visibility diving. Seeing an arms length only is not unheard of and we can handle lost visibility too. Some of us have done recovery dives where the initial visibility has been a few millimetres only. We believe that diving like this can only be mastered through practice (and certainly not after a PADI course). Fortunately, we are a bunch of adults who know their limits - no heroes here Here's a link to some old pictures of diving in our local river in 2012: http://www.ts.fi/uutiset/kotimaa/390642/Romunsukeltajat+tormasivat+yllatysloytoon+Aurajoessa#

The reason why we want to avoid silting is that seeing an arms length really makes a huge difference. If the visibility is totally lost, then in addition to searching the bottom one needs to sweep the water in front of oneself to avoid protruding objects. This makes searching slow and causes unnecessary risk. Entanglements with bicycles also become a whole lot more "interesting" then.

We got officially approved training for this and we have contact with another group (that even does urgent rescues) that gives us advice when we call. A visit to the local fire brigade is also planned to meet their divers.

We are now in the process of familiarizing ourselves with various sites, mapping them, and choosing appropriare methods for each. It is interesting to read this forum at this point.

I would possibly try a JACK STAY search pattern, and set it up using snorkelers or 2 extra divers, if a boat is unusable in that situation. The JACK STAY, will be the most practical for decompression purposes (doing deep part first), and is a great technique for searching an area methodically, making sure not to miss anything. The surface divers or snorkelers can also be used as tenders.

Not a bad idea. Will try that next

Another great technique is a half moon circle search. Similar to to a full circle search but you would stop the diver after the 180 degree turn.

Oh, true. Using one type of search for the shallows and then sector searches / half moon search at the steeper part. Nice idea.