Today I was looking at the engine and I noticed a lot of salt deposits on the cooling water seacock. Looking closer, the salt was building up where the hose from the engine was connected. Tried the two jubilee clips and they seemed loose. So I thought I would tighten them up. Gave the hose an experimental firm tug.

The hose fell off in me 'and. Honest.

The hose spigot to 1/2" adapter had snapped between the two clips. It had dezincified. As far as I can tell from the wreckage, the metal had lost zinc through about 1mm of thickness from the inside. About 5 years old. Been in the sea for about three years solid in recent years.

It was not electrically connected to anything, apart from the skin fitting, and the the seacock which has a stainless ball in it.
Oh well - I caught it in time.

It was an Aladdins cave brass fitting. Replaced with another. Cheap.

I experimentally hit the remainder of the spigot with a hammer and it bent rather than crumbled.

I will have the boat out for the first time in three years later this summer and I will check out the through hull fittings then.