Was in a boat that sank the other day off Coles Bay. I had an GME MT410G PLB in my lifejacket pocket.
We got rescued before I needed it. When I took the PLB out and tested it I found that there was water inside and that it failed the test function after about an hour in the water.
The next day it self-activated and I had to take it apart to disable it.
They’re supposed to be IP67 rated i.e waterproof to 1m.
A google search shows that a few people have had problems with them leaking and either failing or self-activating.
Thought I’d mention it as it’s a popular model that a lot of people carry, not necessarily in a drybag or a waterproof case.