Leaving a line arrow as an indication of which way you left for a lost buddy is a dangerous practice. In a stressful situation, both time-stressed and situationally-stressed a mistake can easily be made by a diver leaving an arrow. It may conflict with arrows already on the line and this could lead to confusion by the lost diver coming upon the arrow or confusion by a future diver.
I don't see a problem leaving a non-directional marker that is well-marked. I have always used old-style outrigger clips that are well-marked and easy to read. I don't see anything wrong with leaving something like Wet-Notes, but I agree that leaving a light or some part of your gear that might be needed for your own exit would be a bad idea.
I would also not remove any properly-installed reels (I think that almost goes without saying). The lost diver coming upon a reel that he knows your team installed would find his stress-level go WAY down once he found it and could see from the way it was installed from which way the team had come. A marker on the exit-side of the reel tie-off (which many divers do as a matter of course) would also help in his escape.
But strobes, lights etc. are just more junk on the diver and more junk on the line, IMHO. I can see the efficacy of such devices in OW diving under the proper circumstances, but there is a well-known protocol to cave diving that it behooves all cave divers to hew to.
Obviously, the questions comes up, "how did you lose your buddy?" In this (PIII) case, these divers apparently didn't follow buddy-protocol and allowed the team to get split up. I've seen some buddy teams very far apart from each other and often far off the line, even in silty, low-flow systems. And that seems to be a common scenario of "lost off the line" buddies. Something occurs to silt the cave and one buddy, who is close to the line, gets on it and the other one doesn't.
Staying close to the line wherever possible and close to your buddy is the best assurance of an intact team on the line if things go South. And speaking of South, carrying a compass isn't a bad idea. I know it seems pointless in systems that twist and turn, but if you've done due-diligence and know the map and the general directions within the cave, it can save your life.
I was in Falmouth many years ago with a buddy, diving there for the first time. Our dive-plan was to go to the first opening or air-turn, whichever came first. We got 3/4 of the way to the duck-under when suddenly she was off the line and quickly ascending! Falmouth is a huge cave. At this point in the cave you can't see any wall or the ceiling, they are all far away in each direction. The only thing you can see is the dark, loamy floor. It was our first year of cave diving and although we had been diving regularly in Peacock and Ginnie and Little River etc., we really didn't have that many full cave dives, less than 100. So I instantly made a mistake. I was afraid she would embolize ascending that fast so I ascended quickly to catch her, exhaling as I ascended. But I forgot first principles, I didn't run a reel off of the mainline.
According to other divers, at this point in the cave, there are large passages or bulges that go off in other directions at roughly 90 deg. to the line I was on. We had been at around 100' I believe on the line. By the time I caught her we were at about 55', in 30' vis, in a huge, dark cave and I still couldn't see the ceiling. In the process of getting her calmed down (it took half-dozen "OKs" before I got one back) I could see we were near a wall that angled up to the ceiling. We got on the wall. There were no projections to tie-off on or to hold, so I communicated to her that I wanted her to hold the line there.
I ran my safety reel straight down to the floor and using my compass determined which way would be 90 deg. to the line and after a single sweep I found the mainline. I tied-off on it, again used my compass to determine the exit, placed a pin on the exit side of the reel, and then went back up. Once we were back on the line, I was dealing with all the played out, loose line, trying to get it bunched up and tied to the reel (there was no way to get it reeled back in) when suddenly she started swimming frantically INTO THE CAVE! I dropped the line on the floor and started after her swimming quickly at a determined pace, but mindful of the depth, not too fast. I caught her just as she saw the duck-under at which point she stopped like she had run into something, arms and legs splayed-out, suddenly aware of what she was doing. She turned, swimming in a panic towards me, eyes wide. I got hold of her as she approached and careful to "OK" the line, I communicated to her to "hold" and we had a short conversation about getting calmed down and "this way is the exit". She didn't need to be told twice and once again swimming fast, I'm sure with no regard with where I was, she headed for the exit.
I stopped at my reel just long enough to remove it and the whole bundle of line and caught up with her sitting at deco depth. We had a long, uneventful deco and needless to say, though she is still a friend, that was our last cave dive together. Later she told me she thought she was going to pass out and so ascended because she thought it was the depth. I think it vertigo from no real references. But to this day she insists she was always in control, despite all the OKs she didn't return to me there up on the ceiling.
After I made an initial mistake, following protocol kept us from being statistics. But it was overly exciting.
Naturally, this isn't exactly the same thing as a lost diver situation, but it's about protocol. Having a well-known and rehearsed protocol kept me calm, following that protocol helped me stay focused and on point. I had my "we're screwed" moment, but knowing I had a solution that applied gave me the confidence to proceed. In retrospect, it doesn't seem all that tough, hovering 50' somewhere above the line in a giant, possibly 4-way cave with low-vis, no markers and a panicky buddy, but at the time I was genuinely worried. The point is, whether lost or looking for someone who's lost, there's a drill and every member of every team should know that drill by heart.
JoeL
