Is there a safe way to dive on a fresh water dock?

[angus99]

We touched bottom in the middle of the channel on the Trent Severn yesterday and I want to inspect my props. With the holiday, it would be Tuesday before we could be hauled and Friday before we’d have any hope of being back underway. If I can confirm that there’s prop damage (plus other things I want to inspect) I may be able to schedule work ahead of arriving at Bayport Marina in Midland and limp on down there.

I’m aware of the potential for shock hazards while diving near docks in fresh water. But I’m wondering if our position on the Dock and other things I’ll describe below would mitigate the risk. I’d appreciate any thoughts from electrically savvy folks on this.

We are on a T-head at the Port of Orillia, which has brand new docks and wiring. Our stern, where I’d dive, is over 50 feet from the nearest pedestal. Even though I have an isolation transformer, I plan to unplug my boat, wait until tomorrow when all of the nearby boats are gone and switch off all the nearby breakers. In other words, I would be hundreds of feet from any plugged-in boats that might be leaking voltage and the boats would be between me and the shore/source of power.

Finally, I would secure myself with a rope, just in case.

I know divers do this all the time in fresh and salt water—and maybe I’m over-thinking it, but I want to be extra cautious.

 

[caltexflanc]

Use a multimeter with some longish cables and see how much voltage and continuity you get . Might give you a small clue. Ask the marina if they are aware of any issues.

 

[CharlieJ]

wait until tomorrow when all of the nearby boats are gone and switch off all the nearby breakers.

A good idea to protect you; a VERY BAD idea from a liability issue. You could cause inadvertent harm by cycling shore power off/on on a neighboring vessel.

Does the marina have ground fault protection devices (GFP) at the pedestal, feeder panel or at the utility entrance? If so, then you are relatively safe.

 

[Maerin]

Are you experiencing any vibration that indicates damage, or did your experience with the bottom include telltale prop noise? The run west from Kirkland is notorious, we contacted the bottom twice, once going through the keyhole bridge. But our full keel protected us, no damage.



If there's no indication of damage, keep in mind you'll be hauled at Lock 44 for free. Perhaps you could contact the lock and see if they'll allow you to have a look. Even if you're not allowed onto the deck, you could hang over the swim deck and take photos then blow them up and inspect them.


Make sure you visit the Mariposa market! Orillia is worth staying a couple days!

 

[tiltrider1]

Angus99, climb on to your swim platform and stick your hand in the water. If there is an issue you will feel it immediately and you will be able to pull your hand out. If you feel nothing then you are good to go under your boat, just don’t head towards any other boat.

 

[angus99]

A good idea to protect you; a VERY BAD idea from a liability issue. You could cause inadvertent harm by cycling shore power off/on on a neighboring vessel.

Does the marina have ground fault protection devices (GFP) at the pedestal, feeder panel or at the utility entrance? If so, then you are relatively safe.

I would never turn off a pedestal with anyone connected to it.

 

[SoWhat]

Borescope should be part of your toolkit. You can inspect the prop without diving on it.

https://www.amazon.com/Depstech-433...=1535903055&sr=1-1-catcorr&keywords=borescope

 

[angus99]

Are you experiencing any vibration that indicates damage, or did your experience with the bottom include telltale prop noise? The run west from Kirkland is notorious, we contacted the bottom twice, once going through the keyhole bridge. But our full keel protected us, no damage.



If there's no indication of damage, keep in mind you'll be hauled at Lock 44 for free. Perhaps you could contact the lock and see if they'll allow you to have a look. Even if you're not allowed onto the deck, you could hang over the swim deck and take photos then blow them up and inspect them.


Make sure you visit the Mariposa market! Orillia is worth staying a couple days!

Thanks. I did ask about being able to inspect at lock 44 and it seems to depend on the crew and how busy they are.

Yeah that stretch really sucks. I have idea how a vessel with more than 5 ft draft navigates it. We do have some vibration and we’re running a half knot slower than we were at the same rpm, leading me to wonder if something got fouled down there.

 

[CharlieJ]

angus99: Good to know; I just want to be sure based on your original post.

How about the presence of GFPs?

This is serious stuff. Note that the latest version of the National Electrical Code requires a warning to be posted at all marinas and private docks:

555.24 Signage. Permanent safety signs shall be installed to
give notice of electrical shock hazard risks to persons using or
swimming near a boat dock or marina and shall comply with all
of the following:
(1) The signage shall comply with 110.21(B)(1) and be of
sufficient durability to withstand the environment.
(2) The signs shall be clearly visible from all approaches to a
marina or boatyard facility.
(3) The signs shall state “WARNING — POTENTIAL SHOCK
HAZARD — ELECTRICAL CURRENTS MAY BE
PRESENT IN THE WATER.”

so you have every reason to be cautious.

A quality voltmeter and probes spaced a known distance can be used to check the water around the boat to see what the AC voltage gradient is. Testing has shown that a gradient of 2 VAC/ft in freshwater is lethal. And of course 0 VAC/ft is the goal.

 

[dhays]

Just to be clear, the question was is there a safe way to give on a fresh water dock. I think the clear answer is NO. As long as there are power pedestals on the dock, I don’t think you can consider it “safe” at all. You can make it safER, but not safe. Much like you can remove rounds from a revolver to make it safer. However, unless you remove all the rounds it isn’t truly safe. Not saying not to dive on the boat using some of the precautions mentioned, just keep in mind that there is still a live round somewhere in the cylinder and it could come up while you are in the water.

 

[menzies]

On our recent Chesapeake trip we bumped once on the way up in the A&P (in reverse), and hit a big log in the Potomac. One the way back we bumped twice. Each time we gradually increased RPM and felt for vibration or other issues. Finding none we carried on.

After getting home I had the diver from Pier 88 Diving come to clean the bottom and I asked him to do the check for me. No issues. Cost $160, no zincs required this time.

Perhaps get a professional diver to come and check for you. They know what they are doing in marinas.

 

[angus99]

A quality voltmeter and probes spaced a known distance can be used to check the water around the boat to see what the AC voltage gradient is. Testing has shown that a gradient of 2 VAC/ft in freshwater is lethal. And of course 0 VAC/ft is the goal.

Thanks.

I used my Fluke multimeter with enough wire to get 10-15 feet of spacing between probes. I then took measurements at various locations and depths around our boat. The meter seems to be baseline-calibrated at .004 volts AC (with probes touching air) and remained unchanged everywhere I measured in the water.

 

[Jeff F]

You may want to limp over to Chief's Island a couple of miles away. There's good anchoring on the south and west side where you can dive well away from sources of stray current and/or other boats.

 

[Comodave]

I guess it comes down to the question, do you feel lucky? The current in the water, if any will probably flow from the boat that is leaking the current to ground which is most likely the nearest shore. Do you have someone to be a lookout? If so make sure they do not enter the water if you have a problem. Usually what happens is not that you get electrocuted but rather the small current flow locks up your muscles and you can’t swim or raise your head out of the water and you then drown. Why not just take your boat out of the marina and anchor somewhere, turn off your genset and then dive and check them out. We had a problem on the TSW with vibration. On the Big Chute the lockmaster removed the weeds and the problem was resolved.

 

[angus99]

We are on a T-head on an enormously long dock. The nearest boat is more than 100 feet away and it’s between us and land. These docks were built and wired within the last couple of years and are very well-maintained. The multimeter does not detect any voltage anywhere near my boat—before I unplug it. I will have an assistant with a boat hook and a rope around me. I plan to enter the water one rung at a time on our swim ladder and pause to feel

I know this may sound risky to some, but I’m taking many more precautions than the professional diver we used in Oswego who simply suited up and jumped in. I don’t want to rely on “luck, but I’m thinking with my boat completely unplugged and no others around, I have done my due diligence. See you guys on the other side if I’m wrong.

 

[dhays]

Despite my earlier comments, I'd do the same thing Angus.

 

[angus99]

Despite my earlier comments, I'd do the same thing Angus.

Thanks, Dave. I’m pretty risk-averse, but I followed the steps above and felt absolutely nothing while I was lowering myself into the water.

Now the good news . . . not a trace of a ding on either prop! What I did find was a jungle of weed wrapped around both shafts and the struts. It was tightly packed and formed a sleeve three to four inches thick around the entire diameter of the shafts. Not sure if all that extra drag contributed to the mild vibration we were feeling or to my missing half knot, but it couldn’t have helped.

I pulled as much off as I could and I’ll ask the guys at Big Chute if I can take a look—as Maerin suggested—while they’re lifting us over the hill.

Thanks to all for weighing in. Feeling some serious relief here.

 

[dhays]

Great news!

 

[diver dave]

This is where i jump in with my dry suit, latex attached hood and snap on dry gloves. [emoji108]

 

[angus99]

This is where i jump in with my dry suit, latex attached hood and snap on dry gloves. [emoji108]

Wish you were here earlier this afternoon.

Seriously, how do pro/experienced divers mitigate the risks of diving near docks?

 

[CharlieJ]

Glad to hear the good news and very glad that you took this situation as seriously as you did!

The threat of electric shock drowning is real in fresh water. Watch the video of my friend Kevin Ritz recounting the death by ESD of his son Lucas. It will break your heart and forever imprint the danger of ESD in your brain.

 

[adornato]

dock diving to check prop

The last time we chartered a boat in Anacortes Washington, the charter company staff used an underwater drone with a camera to check the prop and rudder when we returned.

(the next thing will be a robo hull cleaner?)

 

[Rip]

You mean like this Boat wash from Drive-in Boatwash™ | Drive-in Boatwash ?

 

[Bigsfish]

We have a GoPro on a long telescoping pole that we can check our props and rudders without gettin in the water. Inexpensive in the long run. I don’t like electric shock treatment although some say I need it.

 

[angus99]

We have a GoPro on a long telescoping pole that we can check our props and rudders without gettin in the water. Inexpensive in the long run. I don’t like electric shock treatment although some say I need it.

Brilliant! Now I know what I’m getting the Mrs. for Christmas.

 

[Bigsfish]

It’s a really good video camera too.

 

[Allan Reese]

You ask about diving on a boat in fresh water. Is it less dangerous to dive in salt water?

 

[dhays]

We have a GoPro on a long telescoping pole that we can check our props and rudders without gettin in the water. Inexpensive in the long run. I don’t like electric shock treatment although some say I need it.

I tried that very thing earlier in the week. It works well. Us you can’t tell where you are pointing the camera. I need a longer pole as well.

 

[Bigsfish]

Dave

You need to put an index mark on the pole so you can tell what direction the lens is pointed. My pole expands (no dirty minds) to about 12 feet, standing on the swim platform makes it easy.

 

[dhays]

Dave

You need to put an index mark on the pole so you can tell what direction the lens is pointed. My pole expands (no dirty minds) to about 12 feet, standing on the swim platform makes it easy.

Ah, good idea. I tried it with a short grip and so was a bit too close. Thinking about it now, I would do it in time lapse mode and high resolution. That way individual photos could be studied carefully and zoomed in on.