Basic Navigation in Spring Lake, San Marcos

[driftwood]

Cruiser said she was interested in me fine tuning her navigation skills in Spring Lake. So here is the basic information that 95% of all divers in the lake will ever need.

Nav is really pretty simple. You have two ways to get from the Training Area to Diversion. Around or under the old submarine theater. From Diversion to Cream of Wheat, over the hump (the preferred path is around the hump to the right) into Cream of Wheat/Little Riverbed.

At the bottom of Little Riverbed, stop and look both ways for boats and the deep passage is about 11 o'clock. This is the most dangerous part of the dive and if you are not careful you can porpoise to the surface. When you look at your choices in LR the path to the right looks deeper but shallows very quickly as you turn to the left.

The basic rule is that you enter Ossified Forrest to the left and exit to the right.

When you leave OF, take the right side and turn left to get into Riverbed. Once in Riverbed straight and clear shot to the bottom of Catfish Hotel.

The run from COW to CH lies on a 50/230 degree bearing. You can use that to get you where you need to be (especially when vis is down due to work) but it doesn't have the finer points for the deep passages.

The next run is from the Landing into Deep Hole and Arch Site. If you cannot find Deep Hole, you have no business being in the lake. A straight run from the Landing to Deep Hole will put you very close to Web Cam and the USGS instrument package (nice way to tell you where to exit DH).

Deep Hole is shaped like a flattened W. The right channel is where we used to go to get to Catfish (now closed to divers). The middle channel is a dead end. The left channel is the one that will get you to Arch Site.

When you are in DH, there are two main high pressure springs. Deep Hole (USGS instruments) and Fault Line. With FL on your left and two low pressure springs ( I call them the "Twins") on your right, take a 270 bearing and that is the passage I cleared to Arch Site. It is twenty - thirty feet long. If that is closed then continue westerly along the channel looking to turn to your left when there is a break in the weeds. If that fails, you will eventually end up at the Dock and Arch Site is basically at your 10 o'clock when you are perpendicular to the dock and facing down stream.

To get from Arch Site to DH go to the east corner of the site and head east from there. You will hit DH. Find the USGS instrument package and head back to the Landing.

One thing I have done is to memorize specific landmarks to tell me exactly where to make my turns getting from one area of the lake to another.

 

[PeppermintPaddi]

just hitting the 'thanks' button is inadequate. had to say - wow!

 

[cruiser]

Very helpful, Jeff. Having dived there about 30 times, I can visualize most of your narrative

 

[idocsteve]

At the bottom of Little Riverbed, stop and look both ways for boats and the deep passage is about 11 o'clock. This is the most dangerous part of the dive and if you are not careful you can porpoise to the surface.

Why would a competent and well trained Scuba diver, with the proper gear including a BCD and depth gauge, porpoise to the surface if they are not careful? At this dive site or any other?

 

[austinspace]

Its a very shallow passage, just a few feet, and we need to stay under at all times because there are boats.

 

[idocsteve]

Its a very shallow passage, just a few feet, and we need to stay under at all times because there are boats.

That explains it!

 

[redacted]

Why would a competent and well trained Scuba diver, with the proper gear including a BCD and depth gauge, porpoise to the surface if they are not careful? At this dive site or any other?

Because the water is only 3 to 4 ft deep so a moments inattention can put you on the surface real quick.

Why would you need a BCD and Depth Gauge?

 

[idocsteve]

Because the water is only 3 to 4 ft deep so a moments inattention can put you on the surface real quick.

Why would you need a BCD and Depth Gauge?

Well, speaking for myself, I use a BCD to maintain my buoyancy and sometimes as a float at the surface while waiting for a pickup or during a swim back to shore; and I use a depth gauge so that I know how deep I am. It makes dive planning a lot easier.

 

[driftwood]

Hi Steve,

Very good question. Let me see if I can explain it in more detail. Both John Payne and me have lost buoyancy control at that exact spot when we had changes in our gear (both times we were using rental BC's while our were being repaired). Between us, we have logged thousands of hours in the lake.

There are a couple of things that make diving in Spring Lake different.

First, it is a constant 72 degrees and a lot of people are comfortable in a 7mm suit. The lake is shallow, maximum depth is 28.5', that makes for long dives which leads to more exposure protection than normal. A 1.5 to 2 hour dive is very possible on an AL 80.

Second, the lake has a lot of suspended solids that make you more buoyant than you would be in most fresh water lakes. The specific gravity of the water is closer to salt water than fresh water. There are a lot of people who do not factor that into their weighting. I dive with 4-5# more lead in Spring Lake than other area lakes due to reasons 1 and 2.

Third, you are very shallow going over that hump, 6' is about right and you are coming up from a 12-14' depth. When I go over that hump, I am literally in the plants and dragging through the mud. I was diving with Austinspace, he didn't keep deep enough. I explained that to him after the dive and he seems to have learned the lesson.

Fourth, Aquarena Center runs glass bottom boat tours. They use college students making minimum wage as tour guides/boat drivers. Just to make it interesting, they love to show the tourists divers in the lake. The boat's prop is around 18" in depth. That leaves you at best 3.5' between the top of your tank and the bottom of the prop at the hump. I ALWAYS stop and look for boats. When I think the coast is clear, I give a full blow to get as negative as possible and swim like I am being chased.

Fourth, part two, the spot we are talking about is a very narrow part of the lake. You can throw a stone across the lake underhanded. The boats traverse that stretch twice on the tour. The second time, they are moving as fast as they can to end the tour and btw, they handle like pigs in a crosswind.

Hope this helps explain my note of caution.