What is this stuff on my hull?

May 22, 2020
12
Pearson 303 Casco Bay
After haulout and power washing, a number of black deposits (see photo) remain on the hull below the waterline. They are quite hard and appear to be on the surface of the antifouling paint, although I have not yet had an opportunity to excavate and see if it is bare lead underneath.

Haven't seen this before--any ideas?
 

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jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,076
CAL 35 Cruiser #21 moored EVERETT WA
No idea. Looks like you sailed through an oil patch.
 
Jan 1, 2006
7,357
Slickcraft 26 Sailfish
What stumps me is the material survived power washing apparently retaining a bulbous shape. Even tar would flatten when hit with power washing.
You might consult a naturalist or biologist.
 
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jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,076
CAL 35 Cruiser #21 moored EVERETT WA
There is this possibility...

Anton Shkaplerov, who will return to the ISS next month, says cotton swabs wiped over the exterior of the station's Russian segment revealed an unidentified life-form that has already been sent back to Earth for scientific analysis.

Could there have been a leak from the lab?:yikes:
 
May 22, 2020
12
Pearson 303 Casco Bay
There is this possibility...

Anton Shkaplerov, who will return to the ISS next month, says cotton swabs wiped over the exterior of the station's Russian segment revealed an unidentified life-form that has already been sent back to Earth for scientific analysis.

Could there have been a leak from the lab?:yikes:
I fully expect to discover that the explanation is both boring and my own stupid fault, but the Andromeda Strain possibility is a lot more interesting...
 
Oct 19, 2017
7,799
O'Day 19 Littleton, NH
Looks like black coral ?
Which opens the question, where has the boat been kept? Black coral is not generally found in shallow northern waters, although it has been found in all oceans at all depths, so maybe.

Perhapse some impurities in the lead pour reacting with the anti-fouling paint or some contaminants in the water reacting with the paint?

-Will
 
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LloydB

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Jan 15, 2006
893
Macgregor 22 Silverton
As we approach Halloween pumpkins warts have began appearing in many unexpected places. Scientist experienced with AI have been forecasting this situation for years as it has to do with the juxtaposition of daylight savings time and the vote caused by the overabundance of black ink formally used by newspapers.
 
May 22, 2020
12
Pearson 303 Casco Bay
illusion1024, anything to report on the excavation?
I spent a bit of time the other day scraping at the stuff without any epiphanies. It is really really hard, which makes me think it is some kind of product of metal corrosion rather than organic, but it sits on top of the antifouling paint. In a few areas, the barrier coat has failed and this stuff did not appear to extend all the way through to the bare lead.

Not a satisfying update, unfortunately!
 
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jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,076
CAL 35 Cruiser #21 moored EVERETT WA
@illusion1024 Thank you for the update. Sometimes, mysteries are just that mysterious.