Deep surge

[FredT]

Wave length is defined by the wave period.
L= 5.12T^2
Water depth where the wave starts to significantly feel the bottom is at approximately half the wave length.

As an example a 6 second wave starts to feel bottom in 92 feet of water while a 16 second wave starts to feel bottom in 655 feet of water.

Speed of the water particles and orbit size is approximately halved for every 1/9 wavelength in depth. A 10' wave with 12 second period has a surface particle circle of 10' in diameter and a wavelength of 1000 ft. At 111 feet (1/9*L) the particle motion of the wave is decreased so the particle motion circle is now 5'. If the bottom is close the circular wave motion is compressed into a elipse with a similar although slightly smaller internal area. This flattened wave particle motion is what divers feel as "surge".

FT

 

[Soggy]

We also had a similar situation here in 100fsw. We called the dive after 10 minutes since there was no visibility and we were getting repeatedly bashed into the wreck. This was also due to a hurricane far far off shore. It was a beautiful, calm day on the surface with only minor swells.

 

[GottaScuba]

Rick as the next post says, I too have experienced such viscious surges at depth. One being the yukon off San Diego where I ws averaging about 85-90 ft and then another wreck in the same general area about a month later the " Ruby E. " She always tends to have a good surge along her Port side for some reason going from bow to stern which lies at about 80 ft max. In my years of diving wrecks around wreck alley off the San Diego coast these surges are not all that uncommon.

 

[Spectre]

We also had a similar situation here in 100fsw. We called the dive after 10 minutes since there was no visibility and we were getting repeatedly bashed into the wreck. This was also due to a hurricane far far off shore. It was a beautiful, calm day on the surface with only minor swells.

I'm guessing that's the same day I was thinking of. It was definately a nice day on the surface, but if you looked close [or sat on the side of the boat in doubles] you would have noticed that the swells were actually pretty big, it's just that the period was so long that it didn't really look like much.

My dive [with notabob and divegary I believe] had planned that notabob wanted to practice running a reel. It turned out to be a very good thing, since a line was definately desired. Depth was about 90 feet, and the wreck would vanish, then appear, vanish then appear, as we had about 4 feet of surge with 3 feet of vis.

Now if your looking for deep surge stories, Eric Fine definately has the best one I've ever heard!

 

[carp8dm]

Last summer we had an interesting sea state that was surprising. There was a hurricane about 500 miles away down in the southern Gulf that was sending a very long period but very large ground swell up to Panama City. Bottom line, there was tremendous surge on the bottom at 80 feet!
It didn't seem like much of a problem until we got down on the site, an artificial reef made of a sunken ocean tug - but there you had to be extremely careful lest you end up with a sudden bruising or cutting trip into some barnacle covered structure or worse, get sucked through a porthole that was a little too small!
Anyone else seen big surge that deep?
Rick

Hi Rick, about 7 years ago i was diving off Lunenburg, Nova Scotia on the Saguenay wreck (s of the Swiss air crash) & i experienced strong surges at 70-90' on the wreck. It was quite amazing.

 

[ericfine50]

Well, since Spectre mentioned it -

A few years ago, I was diving off of the Eagles Nest out of NY and we were on the Stolt Degali. There was some current on the surface and we make our way down to the wreck. Surge is strong, and I am going over the top, all of a sudden - the surge takes me and whipe me inside of the wreck (stairwell/cargo area) and back out again. Not fun - Thumbed the dive and went back.

Eric