Black witch and a patch, sorted.
I've just spent the last couple of hours scraping the hull of a fishing boat.
And discovering that my drysuit has a 10mm split in the left hand cuff. I is damp.
As a temporary fix. It'll get neoprene seals in the long run. They might not be as watertight but they last longer and don't fail suddenly IME.
The right boot could also be with being one size bigger and the whole suit is a touch snug so, as ever, I'll be scouring Ebay.