Northwest Dive Club

Im curious to know how people estimate the visibility on a given dive. I know its pretty subjective but Ive seen it extremely over rated and extremely under rated. For example Ive been at Cove 2/Muk/InsertDiveSiteHere and asked a diver "hows the vis?" and get back "30-40 feet" then I get in the water and can't see 10 feet. I mean if I can see the silloutte of a seal 20ft away does that mean the vis is twenty feet? even if I can't really tell if the shadow is a seal or my mother in law?

You would actually be surprised how the viz changes here in some of the sites, even throughout the day.
This usually depends on tides (incoming/outgoing), currents, weather, river runoff and number of divers (dive activity) and believe it or not, seals showing up for a dive. These are just some common variables.There are more!
If I hear the viz was not too bad, then I figure 20-25ft range. Great viz is 35/40ft plus.
One thing to note. If it is mucky, yucky the first 10 to 20ft, it may open up at depth to a nice 20ft or so.
I just get in and dive!!!
Kirsten

Scubak wrote: This usually depends on tides (incoming/outgoing), currents, weather, river runoff and number of divers (dive activity) and believe it or not, seals showing up for a dive.
Kirsten

I know it varies, its ultimatly my goal to be able to look at my dive log (or maybe someday memory) and learn whats best at what time of year, current, whatever. It doesn't help though when I ask others and their numbers are way outta wack with my own.

all vis reports need to be taken with a huge grain of salt. With that said, if the person who is posting the report has extensive experience at a site and knows how far apart the "landmarks" are and is judging visibility based on those fixed landmarks then the grain of salt gets a little smaller. This is coming from a guy that just started diving this mud again after an 8 year exile to asia with 100ft vis as routine, here every dive so far has been akin to a night dive with old batteries in my light.

My personal barometer is how far away can I see a diver (minus any HID light etc). Not necessarily recognize (if I see my 87yo mother in law I KNOW I'm narced!!), just know they are a diver and their rough orientation to me. That distance is "the vis", I round down so I rarely have "40ft" days, few times a year at best. Using this yardstick, average Alki vis is about 15ft IMHO.

The most important distinction is horizontal vs. vertical viz.

Vertical is always greater -- last week I could see surface ripples from 90ft at Cove II, but the horizontal viz was only about 40ft. I usually try and fixate on an object and then see how many diver lengths it takes to get there. Took me about 6-7 lengths = 40 ft.

If anyone tells you cove II was 60 ft, then they probably saw a 24 ft Sixgill too

lundysd wrote:If anyone tells you cove II was 60 ft, then they probably saw a 24 ft Sixgill too

I've seen Cove 2 like that... once... but must have missed the sixgill. I could see the i-beams from a deceptively long distance away... it was weird and very cool all at once.

I'm horrible at judging vis. For me it's either bad, normal, good, or great... and I can't tell you where those lines are. It's just, yeah. I have experienced what Lundy's talking about too - vertical vis being much better than horizontal vis. Is that real or is that just because the sun is sending light your way so there is no back-scatter/reflection on the bad vis coming toward your eyes?

Most divers around here wouldn't know what 10 feet of vis was if it cooked them breakfast. I've had everything from "can't read my compass when it's pressed against my mask" viz up to, no kidding, 60-70' of horizontal vis, here in the Sound. Up in Canada was the first time I saw legit 100' visibility, and it blew my mind.

Visibility reports are pretty subjective. It helps to know the person you're asking. When I'm asking someone I don't know, I just ask if the vis is "good" or "bad".

My yardstick is how far away I can see AND identify my dive buddy. Not just know he is there but know it is him from the gear he is wearing. I too have had those days where you almost had to hold hands and I have seen a couple days where I could see an honest 50 to 60 ft. I had one day at TTN where I didn't need a light at 115 fsw and I could actually see two or three of the tire piles at once!

Before the Seahurst website went down, I saw how they determined vis. They had black and white round reflective markers set-up at 5’ or 10’ increments from the camera. You could just count the markers and tell before you would dive. I think that is a cool idea, and it wouldn’t take much to set something like that up at your local site. Just a few stakes at equal intervals and a starting point to view from, and you have a good gauge!

I doubt my viz estimates are accurate, but I have a rough yardstick. It's based on a very unscientific set of criteria, involving how clearly I can see my buddy, and how much warning I have before I swim into something.

Below 10': I have to swim with my nose no more than 18" off the bottom, to see the bottom. I almost swim into things before I know they're there. I have aborted these dives.

10': I can see my buddy, but if we're on opposite sides of a piling, he's indistinct. Things loom up in front of me as big, dark blurs.

15': He can stop and look at something, and I can turn around and still see something besides bubbles and the glint off a tank. Things actually begin to resolve into shapes before I can touch them.

20: Normal viz. No stress keeping a team together; I can see some details of objects from 10' or so away.

30: Good viz! Some ambient light at medium depths. I can see one set of pilings in Cove 2 from the previous set, or one attraction at Edmonds from another. Divers are recognizable as individuals as they approach.

40': Wide open. Terrain underwater becomes a panorama instead of a snapshot. Good ambient light at medium depths. These are special days.

I've had one day at Cove 2 where I'd estimate the viz was 60' or more -- you could literally see across the cove from the boundary line to the pilings, and it was amazing to get a total gestalt of the site layout (and realize how close things really are together!) We spent 80' in the water that day, and I saw my SPG in the red for the only time ever, chasing a jellyfish in 6' of water, because neither of us wanted to end the dive.

lundysd wrote:The most important distinction is horizontal vs. vertical viz.

Vertical is always greater -- last week I could see surface ripples from 90ft at Cove II, but the horizontal viz was only about 40ft. I usually try and fixate on an object and then see how many diver lengths it takes to get there. Took me about 6-7 lengths = 40 ft.

If anyone tells you cove II was 60 ft, then they probably saw a 24 ft Sixgill too

I've had days (rare, but they happen) when you could look down the entire length of the I-beams and make out the anemones on the one that's standing up almost vertically behind the other two ... and a dive light was completely unnecessary.

Not sure how to rate vis like that ... I just log it as "freak'n awesome!"

... Bob (Grateful Diver)

sheahanmcculla wrote:Before the Seahurst website went down, I saw how they determined vis. They had black and white round reflective markers set-up at 5’ or 10’ increments from the camera. You could just count the markers and tell before you would dive. I think that is a cool idea, and it wouldn’t take much to set something like that up at your local site. Just a few stakes at equal intervals and a starting point to view from, and you have a good gauge!

At what depth?

It's common to have poor vis at one depth and very good vis on the same dive at a different depth.

I have logged several dives where, in the "vis" column the range went something like "3 to 30 feet".

... Bob (Grateful Diver)

I won’t be making any vis estimates for awhile because I am finally getting a prescription mask and I am afraid my vis reports will be wildly off in near future.

This is an interesting thread. Each diver's assessment of viz on any given day/dive site is a lot like asking five different divers the best way to do "X". Usually, you'll get five different answers (unless you're asking a group of UTD divers ).

When I ask about viz, I'm usually satisfied if someone just says "good" or "bad" or something else, rather than giving me an XX foot estimate. If they say "awesome" then I'm estatic. Yes I know that is just as subjective, but hey, I suck at estimating distance myself so I don't expect accuracy from others. Full disclosure: I'm sure I've given some incredibly unbelievable distance reports to some of you out there in the past, simply because I was so excited to be able to see beyond the end of my arm.

From now on, I'm sticking with few standard responses:

It sucks
It was ok
It was good
It was freakin' awesome!

lizard0924 wrote:This is an interesting thread. Each diver's assessment of viz on any given day/dive site is a lot like asking five different divers the best way to do "X". Usually, you'll get five different answers (unless you're asking a group of UTD divers ).

When I ask about viz, I'm usually satisfied if someone just says "good" or "bad" or something else, rather than giving me an XX foot estimate. If they say "awesome" then I'm estatic. Yes I know that is just as subjective, but hey, I suck at estimating distance myself so I don't expect accuracy from others. Full disclosure: I'm sure I've given some incredibly unbelievable distance reports to some of you out there in the past, simply because I was so excited to be able to see beyond the end of my arm.

From now on, I'm sticking with few standard responses:

It sucks
It was ok
It was good
It was freakin' awesome!

LOL ... that's similar to how I measure octopus sizes. There are four standard measurements ...

Tiny
Kinda small
Medium sized
Really f@!kin' HUGE!

... Bob (Grateful Diver)

Grateful Diver wrote:I have logged several dives where, in the "vis" column the range went something like "3 to 30 feet".

... Bob (Grateful Diver)

Last night at EUP, for example. It was 5 to 20 feet, depending where in the park you were...

LCF wrote:I've had one day at Cove 2 where I'd estimate the viz was 60' or more -- you could literally see across the cove from the boundary line to the pilings, and it was amazing to get a total gestalt of the site layout (and realize how close things really are together!) We spent 80' in the water that day, and I saw my SPG in the red for the only time ever, chasing a jellyfish in 6' of water, because neither of us wanted to end the dive.

That brings a tear to my eye, it's so beautiful!

Is there any "official" way to estimate the viz? I can see my buddies outline or I can ID my buddy or ? It seems like it varies by the estimator. Maybe Joshua can put on a class so we can all do it the same. I do like the rating categories listed here (it sucks, o.k., good and fantastic.) You can add one to the bottom of the rung "I can't see!!"

Good viz = I can see past the nose of the scooter
Bad viz = Buddy's light is a faint glow.

With all these varying degrees of visibility, it just goes to show that you can have 5 divers dive the same place and the same time and get 5 different dives and reports.

K