Knots.......

[texdiveguy]

..........Just always find it interesting to hear divers say "I was diving at _______ in a '5' knot current".......... how is it they know what knot the underwater current was flowing??? hmm I am a (non/mild/ripping) current diver. Just always find this 'knot' statement curious......again just this weekend I was visiting with a group of rec. divers, and one fellow says he was diving in the Flower Gardens NMS off the Texas coast in a "7 knot" current at 80fsw. OK---what did I miss in my dive training---lol..???

PS--I understand fully knot vs mph and distance of travel,,,,and there are all sorts of methods of guestimating 'surface' current speed......my curiousity is conserning underwater currents.

 

[Packhorse]

Maybe when the return to the boat they up anchor and then measure their drifting speed on GPS.

 

[Wildcard]

Or maybe they are sailors who understand these things? Prolly not if they were thinkin they were diving in 7kts.... Same people who dive on vacation only and claim 200 dives a year?

 

[Packhorse]

Same people who dive on vacation only and claim 200 dives a year?

Now thats what I call a vacation!

 

[Wildcard]

ya.There was a thread a while back about "who does 200 A year" Some kid who did weekend dives and a couple of vacations, he claims 200/yr. Tried to tell us he was doing 7 tanks a day on vacation..... Narced on the surface IMHO.

 

[Whale Whisperer]

7 Knots huh? The Gulf Stream 50 Nautical Miles off the East coast sets a drift from 6 Knots to 9 Knots due north anywhere from the surface to as deep as 200' or more (Don't ask me how I know this). I'd belive it in they were diving in a fast narrow river, the gulf stream or a rip tide...

 

[victor]

http://tidesandcurrents.noaa.gov/faq4.html#70

Q: Where are the fastest tidal currents?

Below is a list of the 50 locations in North America with the fastest tidal currents.
Station Name Latitude Longitude Speed(knots)
Flood Ebb

Seymour Narrows 50 8.00N 125 21.00W 9.2 9.8
Hole In The Wall, Okisollo Channel 50 18.00N 125 13.00W 7.5 7.5
Arran Rapids, north of Stuart Island 50 25.00N 125 8.00W 7.0 7.0
Surge Narrows, Okisollo Channel 50 14.00N 125 10.00W 7.0 7.0
Deception Pass, (Narrows) 48 24.37N 122 38.58W 5.2 6.6
Rapids, near Barnes Bay, Okisollo Channel 50 19.00N 125 16.00W 6.5 6.5
Race Point 50 7.00N 125 20.00W 6.5 6.5
Seechelt Rapids 49 45.00N 123 55.00W 6.5 6.5
Turn Point, Kootznahoo Inlet 57 30.00N 134 35.00W 6.9 6.1
Whirlpool Rapids, Wellbore Channel 50 27.00N 125 47.00W 6.0 6.0
South Inian Pass 58 13.00N 136 21.00W 3.5 6.0

Sorry cannot get then to align up properly.

The gulfstream as a max velocity of 2m/s or about 4 knots however that drops off rapidly the deeper you go or the closer to the edge you are.
http://kingfish.coastal.edu/gulfstream/p2a.htm

I cannot imagine drift diving in a 7 knot current, talk about flags on the pole at the decostop.
On the west coast of wales there is a tidal current like this. It produces a 3ft step in the water which is great fun in a big powerful rubber duck but would be so dangerous to dive in.

 

[Whale Whisperer]

The gulfstream as a max velocity of 2m/s or about 4 knots however that drops off rapidly the deeper you go or the closer to the edge you are.
http://kingfish.coastal.edu/gulfstream/p2a.htm

I cannot imagine drift diving in a 7 knot current, talk about flags on the pole at the decostop.
On the west coast of wales there is a tidal current like this. It produces a 3ft step in the water which is great fun in a big powerful rubber duck but would be so dangerous to dive in.

I've personally encountered 6 Kts at deeper than 200' while navigating across the Gulf Stream. It's quite strong, and requires alot of crabbing!

I've been told that currents above 4-6 kts would be enough to rip your mask off if you were to be stationary. I don't think I'd personally test that theory, maybe mythbusters could do a segment on that?

 

[Charlie99]

I've personally encountered 6 Kts at deeper than 200' while navigating across the Gulf Stream. It's quite strong, and requires alot of crabbing!

How did you measure 6kts? Were you on a 4 kt scooter?

 

[The Kraken]

Swimming against a 7 knot current and going nowhere would br equivalent to running a 10 minute mile. That's moving forward at 8.8 feet per second.

I dare say there are, indeed, very few scuba divers who can swim that fast, even with Jet Fins.

the K