djcheburashka
Contributor
This was not quite a "near miss" -- everyone involved remained calm at all times, no-one was in real trouble. But there's an interesting aspect to it, which is that two divers with very different gear experienced almost exactly the same things in identical conditions. So there's some benefit in considering what happened for each and for the boat, as well as what each perceived and how each reacted.
Overview
The boat tied into a wreck in middling current. (I'm an ok swimming and I could beat the current over short distances but not sustain the pace.)
35 minutes into the dive, Diver 1 (me) did a free ascent 1/2 to 3/4 of a mile directly down current of the boat. Diver 1 was equipped with a yellow XS Scuba 7' bag, 5" in diameter. About 5' of the SMB was inflated at the surface.
Approximately 5-10 minutes later, Diver 2 did a free ascent 100-200 yds closer to the boat than Diver 1. Diver 2 was equipped with an off-brand 4' long, 3" diameter, orange SMB.
Diver 1 reached the surface as the sun was setting. The boat arrived to pickup the divers (who had by then joined) approximately 40 minutes after Diver 1 surfaced. The two divers were about 1.25-1.5 miles from the boat when it lifted anchor and headed toward them. By that time, while not yet pitch black, it was close. Both divers lost sight of the boat below the horizon 10 minutes or so before they were picked up. It was visible to both divers before that time.
Diver 1
Diver 1 used the large yellow buoy because of testing performed by a group that reported (on DIR Explorers) that all SMB's and "barbecue bags" they tried were identically visible from the boat, except that in substantial rain a large yellow SMB was superior the others. However this testing was done during the day, by a team used to team-based free-ascent decompression.
Inflating the bag using a regulator second stage to 4-5' was not difficult, however as the bag became longer on top, it tended to flop over more, and became harder to control. Diver 1 attempted to keep the bag lifted straight-up out of the water, by holding it underwater while at the surface. This could be done, but required an expenditure of effort and periodic breaks. (Note that it is not at all difficult to fully inflate the same SMB from depth and hold it vertically during a free ascent -- the difficulty arose because it was hard to maintain downward tension on the SMB once at the surface.)
As it began to get dark and the boat became harder to make out, Diver 1 turned-on his primary light, a 21-watt DIR-style canister light. Diver 1 alternated between aiming the light directly at the boat, trying to put it underneath the SMB to light it from within, and trying to aim it at the SMB so as to highlight the reflective panels on the top.
Shortly after turning on the light, Diver 1 began to see light flashes from the boat. It appeared that the boat was signalling Diver 1. The signal did not have a pattern - sometimes two flashes, sometimes it was sustained, sometimes several pulses, sometimes breaks. Diver 1 believed the boat was either 1) trying to signal that the boat saw Diver 1, or 2) trying to signal that the boat did not see Diver 1. Diver 1 therefore responded by aiming his light directly at the boat, or from side to side around the boat, to indicate his location and/or signal that he had received the boat's message.
As it became quite dark and the boat disappeared beyond the horizon, Diver 1 became concerned that the boat had lost visual contact with him, and therefore focused on maintaining the SMB in a vertical position and illuminating it with his light.
Shortly after the boat disappeared from view there were more light flashes from the boat, to which Diver 1 responded.
Shortly after that, a bright red vertical light appeared. Diver 1 believed that the boat was doing something unusual to signal its location - almost like a flare.
A few minutes later, Diver 1 saw Diver 2, and that he had an orange SMB. He swam toward Diver 2 and the two met just before the boat picked them up.
Diver 2
Diver 2 was aware of both Diver 1 and the boat as soon as he surfaced. Diver 2 inflated his SMB orally, inflated it fully, and held it either upright from the water or waved it with his hand.
As it got dark, Diver 2 began signalling to Diver 1 with his light, just to communicate and see if they wanted to meet. This is what Diver 1 thought was coming from the boat.
Diver 1's SMB was visible to Diver 2 at all times.
After it got dark, Diver 2 several times illuminated his SMB by holding his light directly up it from the bottom and held the two up. This is what Diver 1 had thought was the the odd flare or light from the boat.
As it got even darker and the boat disappeared from view, Diver 2 headed toward Diver 1, figuring that it made sense to meet up and it was better to swim with the current than against it.
The Boat
The boat had visual contact with bother divers' SMBs at all times, and saw all light flashes aimed at the boat. The boat never did anything to try and communicate with the divers, believing (correctly) that both divers would know that if they weren't on the surface by the time everyone else was the boat would pull anchor and head down-current.
Neither was more visible than the other. With one exception: when Diver 2 illuminated his SMB using his light, this was highly visible and stood out extraordinarily well. Several people on the boat commented that it made Diver 2 very easy to spot. While the boat had consistent line of sight with Diver 1's SMB, Diver 1's attempt to illuminate the SMB with his light were never visible to the boat. The boat never noticed.
Summary
Diver 2's SMB, made from thin, cheap urethane (or plastic or whatever), was easily and strongly illuminated by his light. Because the SMB was so small, Diver 2 was able to wave it above his head with his hand. The SMB was easy to inflate at the surface and control for an extended period of time.
Diver 1's SMB, made from thick, high-quality urethane (or plastic or whatever), neither reflected light well nor could it be illuminated by holding a light underneath. The urethane (or whatever) was too thick. The larger SMB was more difficult to inflate and control at the surface.
There was no difference, to the boat, in the visibility of either SMB, and the boat was able to maintain visual contact with both after the boat had passed beyond the horizon and the divers' view. The divers' SMBs were visible even when flopped on the side and not held upright.
Diver 2's SMB was not, however, visible to Diver 1 (who was at rather than above the surface) until it was illuminated, and then it was not evident what the SMB was. Diver 1's SMB was clearly visible to Diver 2 and identifiable as an SMB at all times.
Diver 1's Change
Diver 1 intends to include in his gear on future night dives a 3', orange, fully closed oral-inflate SMB (from Deep Sea Supply), which (on test) does illuminate with a light held directly underneath. Diver 1 had previously thought of this as a "training" bag, useful for beginning divers because it is easy to orally inflate while controlling buoyancy at depth, but not at all useful for ocean diving because of its small size.
Overview
The boat tied into a wreck in middling current. (I'm an ok swimming and I could beat the current over short distances but not sustain the pace.)
35 minutes into the dive, Diver 1 (me) did a free ascent 1/2 to 3/4 of a mile directly down current of the boat. Diver 1 was equipped with a yellow XS Scuba 7' bag, 5" in diameter. About 5' of the SMB was inflated at the surface.
Approximately 5-10 minutes later, Diver 2 did a free ascent 100-200 yds closer to the boat than Diver 1. Diver 2 was equipped with an off-brand 4' long, 3" diameter, orange SMB.
Diver 1 reached the surface as the sun was setting. The boat arrived to pickup the divers (who had by then joined) approximately 40 minutes after Diver 1 surfaced. The two divers were about 1.25-1.5 miles from the boat when it lifted anchor and headed toward them. By that time, while not yet pitch black, it was close. Both divers lost sight of the boat below the horizon 10 minutes or so before they were picked up. It was visible to both divers before that time.
Diver 1
Diver 1 used the large yellow buoy because of testing performed by a group that reported (on DIR Explorers) that all SMB's and "barbecue bags" they tried were identically visible from the boat, except that in substantial rain a large yellow SMB was superior the others. However this testing was done during the day, by a team used to team-based free-ascent decompression.
Inflating the bag using a regulator second stage to 4-5' was not difficult, however as the bag became longer on top, it tended to flop over more, and became harder to control. Diver 1 attempted to keep the bag lifted straight-up out of the water, by holding it underwater while at the surface. This could be done, but required an expenditure of effort and periodic breaks. (Note that it is not at all difficult to fully inflate the same SMB from depth and hold it vertically during a free ascent -- the difficulty arose because it was hard to maintain downward tension on the SMB once at the surface.)
As it began to get dark and the boat became harder to make out, Diver 1 turned-on his primary light, a 21-watt DIR-style canister light. Diver 1 alternated between aiming the light directly at the boat, trying to put it underneath the SMB to light it from within, and trying to aim it at the SMB so as to highlight the reflective panels on the top.
Shortly after turning on the light, Diver 1 began to see light flashes from the boat. It appeared that the boat was signalling Diver 1. The signal did not have a pattern - sometimes two flashes, sometimes it was sustained, sometimes several pulses, sometimes breaks. Diver 1 believed the boat was either 1) trying to signal that the boat saw Diver 1, or 2) trying to signal that the boat did not see Diver 1. Diver 1 therefore responded by aiming his light directly at the boat, or from side to side around the boat, to indicate his location and/or signal that he had received the boat's message.
As it became quite dark and the boat disappeared beyond the horizon, Diver 1 became concerned that the boat had lost visual contact with him, and therefore focused on maintaining the SMB in a vertical position and illuminating it with his light.
Shortly after the boat disappeared from view there were more light flashes from the boat, to which Diver 1 responded.
Shortly after that, a bright red vertical light appeared. Diver 1 believed that the boat was doing something unusual to signal its location - almost like a flare.
A few minutes later, Diver 1 saw Diver 2, and that he had an orange SMB. He swam toward Diver 2 and the two met just before the boat picked them up.
Diver 2
Diver 2 was aware of both Diver 1 and the boat as soon as he surfaced. Diver 2 inflated his SMB orally, inflated it fully, and held it either upright from the water or waved it with his hand.
As it got dark, Diver 2 began signalling to Diver 1 with his light, just to communicate and see if they wanted to meet. This is what Diver 1 thought was coming from the boat.
Diver 1's SMB was visible to Diver 2 at all times.
After it got dark, Diver 2 several times illuminated his SMB by holding his light directly up it from the bottom and held the two up. This is what Diver 1 had thought was the the odd flare or light from the boat.
As it got even darker and the boat disappeared from view, Diver 2 headed toward Diver 1, figuring that it made sense to meet up and it was better to swim with the current than against it.
The Boat
The boat had visual contact with bother divers' SMBs at all times, and saw all light flashes aimed at the boat. The boat never did anything to try and communicate with the divers, believing (correctly) that both divers would know that if they weren't on the surface by the time everyone else was the boat would pull anchor and head down-current.
Neither was more visible than the other. With one exception: when Diver 2 illuminated his SMB using his light, this was highly visible and stood out extraordinarily well. Several people on the boat commented that it made Diver 2 very easy to spot. While the boat had consistent line of sight with Diver 1's SMB, Diver 1's attempt to illuminate the SMB with his light were never visible to the boat. The boat never noticed.
Summary
Diver 2's SMB, made from thin, cheap urethane (or plastic or whatever), was easily and strongly illuminated by his light. Because the SMB was so small, Diver 2 was able to wave it above his head with his hand. The SMB was easy to inflate at the surface and control for an extended period of time.
Diver 1's SMB, made from thick, high-quality urethane (or plastic or whatever), neither reflected light well nor could it be illuminated by holding a light underneath. The urethane (or whatever) was too thick. The larger SMB was more difficult to inflate and control at the surface.
There was no difference, to the boat, in the visibility of either SMB, and the boat was able to maintain visual contact with both after the boat had passed beyond the horizon and the divers' view. The divers' SMBs were visible even when flopped on the side and not held upright.
Diver 2's SMB was not, however, visible to Diver 1 (who was at rather than above the surface) until it was illuminated, and then it was not evident what the SMB was. Diver 1's SMB was clearly visible to Diver 2 and identifiable as an SMB at all times.
Diver 1's Change
Diver 1 intends to include in his gear on future night dives a 3', orange, fully closed oral-inflate SMB (from Deep Sea Supply), which (on test) does illuminate with a light held directly underneath. Diver 1 had previously thought of this as a "training" bag, useful for beginning divers because it is easy to orally inflate while controlling buoyancy at depth, but not at all useful for ocean diving because of its small size.
