This is an oversuit which is used a lot for cave diving in the Dales. (It has been worn throughout all the time we were working on the Malham Cove project, for example.)
I wear it over drysuits, mainly to protect the (across the shoulders) waterproof zips, which are criminally expensive to replace (hence the obvious protective layer across the back). The oversuit has been in use since the early 1990s and is still going. They often laugh at how scruffy I look but it's saved me thousands of pounds (literally) in replacement drysuits over the years. In my defence, cave diving isn't a fashion parade!
The many tiny dark blobs within the parts coverd by Sikaflex are small areas where the Sikaflex eventually wore through, which are then easily made good with Aquasure. (This is preferable to keep applying Sikaflex generally, otherwise the oversuit starts to become heavier.)
The Sikaflex (the grey stuff) was applied around 8 years ago - and this oversuit really gets hammered in some gnarly places. (I prefer the black Sikaflex but when I needed to apply some last time they only had grey colour in stock at Naylor Myers builders' merchants in Bentham).
Anyway, I rest my case . . . .