How do you aproximate amount of Vis?

BASSMAN · Post by **BASSMAN** » Sat Feb 02, 2008 6:14 am

Brought this over from another thread talking about amount of vis at a particular dive site.

It all seems so relative.

20 foot of vis to me, might be 30 or 15 to someone else.

I mean, how can someone determin amount of vis on a night dive?
Wouldn't it depend on if he or she is diveing with a SL6 as a primary, HID Light Cannon or a Salvo 25 Watt {eyeball burner!!!}

In my log, if I'm logging a night dive, I do not specify amount of vis I just insert "Night Dive"

Could say the same for a Les Davis dive over 60 fsw too!

Just wondering dropping down to a certain depth and looking up to see surface definition. Could that be an accurate way of telling the amount of vis on a particular dive?

I remember doing a dive up in Sitka, where I was down 85 feet and could clearly see the bootom of the boat, as if I was at the deep end of a swimming pool.

That by far, has been the best Vis, I have seen.

I'm looking fwd to more input on this.

Joshua Smith · Post by **Joshua Smith** » Sat Feb 02, 2008 7:39 am

You just need a powerfull enough light! Look and see how far away your light beam will illuminate the bottom, and estimate the distance. (It's pretty subjective, you're right.)

Tom Nic · Post by **Tom Nic** » Sat Feb 02, 2008 9:05 am

I see folks referencing "Horizontal Viz".

I know that on amazing viz days I've seen the surface from 70 fsw, but Horizontal Viz was certainly not 70'.

It might be interesting to play with a tape sometime and check distances with a buddy.

nice-diver · Post by **nice-diver** » Sat Feb 02, 2008 9:30 am

I have wondered the same thing. To me the viz varies if the water is bright or dark, they have a different feel. A "bright" water feels like viz is 15 feet when the actual viz may be only 8ft. I have dove high mountain lakes where you could see the other side of the shore 300ft away...fun fun.

dwashbur · Post by **dwashbur** » Sat Feb 02, 2008 9:32 am

I usually look at my buddies or objects under the water and try to figure out how far away they are and how well I can see them. It's pretty much the SWAG method, but it works for me.

LCF · Post by **LCF** » Sat Feb 02, 2008 9:49 am

Oh, I'm horribly inaccurate, I'm sure. I use a very subjective system . . . If I can see well enough to navigate without using my compass at all, the viz is at least 30 feet. If the viz is pretty good, but my buddy gets a little hazy if he's on the other side of the wreck or the pilings, it's in the 20 - 25 foot range.

If I start getting anxious about opening up any separation between us, it's about 10 feet. Below that come "keeping my nose on Jetty Way because if I'm three feet off the bottom, I can't see it," and "Lake Washington".

sparky · Post by **sparky** » Sat Feb 02, 2008 10:45 am

I use a complicated formula of where by I drop down to a known depth and look up ant the surface to see how much detail I can discern from depth

then I look at a object or structure under water and try determine how far I am from that object . I know that I am 5" 7 and 1/2 inches tall so after swimming to the selected object careful to keep track of the number of my body lengths i had to swim to get there I average to two measurements out and

I Just GUESS $\:D/$

Sparky

Zen Diver · Post by **Zen Diver** » Sat Feb 02, 2008 5:51 pm

This makes me chuckle. Wylerbear and I are always widely differing in our respective viz estimations.

I generally try to estimate how many "Val Units" (ie, 5 feet plus fins) away from a fixed object I am when trying to estimate.

-Valerie

gcbryan · Post by **gcbryan** » Sat Feb 02, 2008 10:01 pm

I don't consider vertical viz so I'm only talking about horizontal. I know that 15' is kind of standard around here and I base everything else off that in a relative way.

If I can only comfortably see what is just ahead it's 10', if it's uncomfortable it's less than 10'. If it's greater than usual it's 20'-25'. If it's better than that it gets more subjective but whatever number I use it's still relative to some known distance.

This all applies to night diving as well as day diving. I'm not measuring how much light I can see but rather how far I can see with decent detail. A bright light doesn't increase viz for the most part unless the viz is just unlimited. Try using a powerful light on a poor viz night. All you will get is backscatter.

Pez7378 · Post by **Pez7378** » Sun Feb 03, 2008 3:09 pm

I lie. I mean, how the hell are you gonna know anyway?

Unless you were there? On my last dive, vis was probably 15 feet at depth (70-95 fsw). It was considerably more visible closer in to shore (15-20 fsw).

Fishstiq · Post by **Fishstiq** » Sun Feb 03, 2008 8:21 pm

Pez7378 wrote:I lie. I mean, how the hell are you gonna know anyway? Unless you were there? On my last dive, vis was probably 15 feet at depth (70-95 fsw). It was considerably more visible closer in to shore (15-20 fsw).

Lie your ass off dude. I got your back!! :rr:

Burntchef · Post by **Burntchef** » Sun Feb 03, 2008 8:25 pm

the second pic of you chris is awesome, true pnw diving

Joshua Smith · Post by **Joshua Smith** » Sun Feb 03, 2008 8:37 pm

Burntchef wrote:the second pic of you chris is awesome, true pnw diving

Yeah- great pics! Only a real diver could appreciate those! :occasion5:

LCF · Post by **LCF** » Sun Feb 03, 2008 9:19 pm

What does it say about me that I look at those pictures and say, "Yeah, NICE trim, streamlined rig, but what's with that SPG?"

Burntchef · Post by **Burntchef** » Sun Feb 03, 2008 9:28 pm

LCF wrote:What does it say about me that I look at those pictures and say, "Yeah, NICE trim, streamlined rig, but what's with that SPG?"

just that you need more in water treatment and less land time :rr:

Sounder · Post by **Sounder** » Mon Feb 04, 2008 7:09 am

LCF wrote:What does it say about me that I look at those pictures and say, "Yeah, NICE trim, streamlined rig, but what's with that SPG?"

You beat me to it - I was going to ask why his fin tips were so far up/vertical in the water in the first picture!

I do really like the second picture... "diver in the mist... with a Salvo!"

Pez7378 · Post by **Pez7378** » Mon Feb 04, 2008 7:52 pm

burntchef wrote:the second pic of you chris is awesome, true pnw diving

Not me, it's Joe. I took the picture though. They were both totally staged. Now I feel like a Fraud!! ](*,)

LCF wrote:What does it say about me that I look at those pictures and say, "Yeah, NICE trim, streamlined rig, but what's with that SPG?"

That my dear Lynne is a 31" hose that does not meet GUE specs!! I asked for a shorter hose and this was all that was available. So, I look at it as my way of "sticking it to the Man"!! But I do have to hold it up when I'm skimming the bottom.

Sounder wrote:I was going to ask why his fin tips were so far up/vertical in the water in the first picture!

That was towards the end of a back stroke......Look how level I am! I noticed the same thing. I blame it on the photographer and his inability to let me get situated. But we had a fantastic dive and visibility was AWESOME..........Just ask us.

Burntchef · Post by **Burntchef** » Mon Feb 04, 2008 7:55 pm

keep stickin it to the man chris!! well not literally i think they frown on that. when are we getting those twins out for some salt?

Pez7378 · Post by **Pez7378** » Mon Feb 04, 2008 8:15 pm

Burntchef wrote:keep stickin it to the man chris!! well not literally i think they frown on that. when are we getting those twins out for some salt?

As soon as I have my P-valve installed.

Burntchef · Post by **Burntchef** » Mon Feb 04, 2008 8:16 pm

let me know, im hoping to be in a new suit myself real soon. gotta love that tax return

Nwbrewer · Post by **Nwbrewer** » Mon Feb 04, 2008 8:28 pm

Pez7378 wrote: That was towards the end of a back stroke......Look how level I am! I noticed the same thing. I blame it on the photographer and his inability to let me get situated. But we had a fantastic dive and visibility was AWESOME..........Just ask us.

Don't let him fool you! His fins always look like that!

Pez7378 · Post by **Pez7378** » Mon Feb 04, 2008 8:32 pm

Nwbrewer · Post by **Nwbrewer** » Mon Feb 04, 2008 8:38 pm

I'm just glad there's no pictures of my pathetic trim around here.

On topic I just guess...

Pez7378 · Post by **Pez7378** » Wed Feb 06, 2008 9:14 pm

Nwbrewer wrote:I'm just glad there's no pictures of my pathetic trim around here.

The visibility this day wasn't too bad. I'd say around 20 feet or so.

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Nwbrewer · Post by **Nwbrewer** » Thu Feb 07, 2008 6:00 am