cmufieldhockey8
Contributor
Background: Dove Hudson Grotto in Hudson, FL with a new buddy.
Dive 1: 62 max depth, 58 min, avg depth 43 ft
1:11 min surface interval
Dive 2: 106 max depth, 59 min, avg depth 46 ft
I figured this is my only chance left to dive Hudson Grotto and I've been there once before but didn't go to the bottom to see the items down there (boats, van.) Another diver who I have dove with was there with his own buddy and had offered to give us a "tour" of the bottom. I wanted to see that stuff before I move up back morth
I talked to my instructor today and he said the reverse profile diving my buddy and I did (63 ft dive then a 106 ft dive) was a no-no. :no If we had done the deep dive first and then the shallower one we would've had a lot more time before the no-deco limit.
I knew that already and that the algorhythm on tables and computers doesn't allow you as much time for your second dive if you reverse profile but I didn't really know why. He told me today it had something to do with the computer and tables not really knowing how much residual nitrogen you've got. I don't remember his exact words, but safety is a factor when doing reverse profile diving.
My reasoning was that I'd never dove with this buddy and wasn't comfortable with our first dive together going so far past his deepest depth of about 60 feet. And Hudson Grotto is so odd with the tannin that the dark water is another factor that could be adding to a potential disaster. My buddy does have a bunch of dives and they weren't in places like Cozumel where the visibility is 100 ft. However 100 foot dives are a big deal to me and I needed a dive with him first.
I thought the benefit of a shallower dive first with my buddy and an opportunity to "feel him out" as a diver would outweigh the cost of diving a reverse profile so thats why I did it. The fact that we jumped so much deeper the second dive is another detail that alarmed my instructor. He also brought up that if we had problems the second dive and either stayed down too long and went into deco or somebody shot to the surface, our tissue already being saturated with nitrogen from the first dive makes that more of an issue then if we had done the deep dive first and developed those problems.
The profile for our first dive was good: started off deepest then got shallower and shallower. We still stayed within no deco limits for the second dive and after we came up from 106 feet we spent 30 min at 40 feet, 10 at 30 feet and 8 at 29 feet so he said that was good.
I did find some some info about a workshop put on by the Smithsonian that says that reverse profile diving is ok as long as you don't go into deco, your max depth is no lower then 130 feet and you don't jump in depth more then 40 feet from dive one to dive two. I jumped 44 feet. It said the only penalty is a shorter bottom time, which my buddy and I definitly noticed and I already knew.
I think the solution to this issue was for me not to do a 100 foot dive. If I wasn't comfortable enough with my buddy to doing the 100 ft dive for the first dive then I'm better off not doing the 100 ft dive then to do what we did. We should've had a longer surface interval too. 1:11 was not nearly long enough.
I have a lot of respect for my instructor- he's got a gazillion dives, he dives 200 ft wrecks (the finest the Great Lakes have to offer) and is a cave diver too. We are very close and most of all he has a very genuine concern for my well being and was not "lecturing" me just to hear himself speak. I definitely learned a lesson and I'd like to pass that on to anybody else.
Dive 1: 62 max depth, 58 min, avg depth 43 ft
1:11 min surface interval
Dive 2: 106 max depth, 59 min, avg depth 46 ft
I figured this is my only chance left to dive Hudson Grotto and I've been there once before but didn't go to the bottom to see the items down there (boats, van.) Another diver who I have dove with was there with his own buddy and had offered to give us a "tour" of the bottom. I wanted to see that stuff before I move up back morth
I talked to my instructor today and he said the reverse profile diving my buddy and I did (63 ft dive then a 106 ft dive) was a no-no. :no If we had done the deep dive first and then the shallower one we would've had a lot more time before the no-deco limit.
I knew that already and that the algorhythm on tables and computers doesn't allow you as much time for your second dive if you reverse profile but I didn't really know why. He told me today it had something to do with the computer and tables not really knowing how much residual nitrogen you've got. I don't remember his exact words, but safety is a factor when doing reverse profile diving.
My reasoning was that I'd never dove with this buddy and wasn't comfortable with our first dive together going so far past his deepest depth of about 60 feet. And Hudson Grotto is so odd with the tannin that the dark water is another factor that could be adding to a potential disaster. My buddy does have a bunch of dives and they weren't in places like Cozumel where the visibility is 100 ft. However 100 foot dives are a big deal to me and I needed a dive with him first.
I thought the benefit of a shallower dive first with my buddy and an opportunity to "feel him out" as a diver would outweigh the cost of diving a reverse profile so thats why I did it. The fact that we jumped so much deeper the second dive is another detail that alarmed my instructor. He also brought up that if we had problems the second dive and either stayed down too long and went into deco or somebody shot to the surface, our tissue already being saturated with nitrogen from the first dive makes that more of an issue then if we had done the deep dive first and developed those problems.
The profile for our first dive was good: started off deepest then got shallower and shallower. We still stayed within no deco limits for the second dive and after we came up from 106 feet we spent 30 min at 40 feet, 10 at 30 feet and 8 at 29 feet so he said that was good.
I did find some some info about a workshop put on by the Smithsonian that says that reverse profile diving is ok as long as you don't go into deco, your max depth is no lower then 130 feet and you don't jump in depth more then 40 feet from dive one to dive two. I jumped 44 feet. It said the only penalty is a shorter bottom time, which my buddy and I definitly noticed and I already knew.
I think the solution to this issue was for me not to do a 100 foot dive. If I wasn't comfortable enough with my buddy to doing the 100 ft dive for the first dive then I'm better off not doing the 100 ft dive then to do what we did. We should've had a longer surface interval too. 1:11 was not nearly long enough.
I have a lot of respect for my instructor- he's got a gazillion dives, he dives 200 ft wrecks (the finest the Great Lakes have to offer) and is a cave diver too. We are very close and most of all he has a very genuine concern for my well being and was not "lecturing" me just to hear himself speak. I definitely learned a lesson and I'd like to pass that on to anybody else.
