A lot of nonsense is being spouted by one or two folks about the amazing water repelling qualities of guernseys/ganseys....whatever.  So I decided to do my very own rather unscientific but nevertheless, "real life" test on the newly knitted sleeve of my latest guernsey.
Facts and figures: 5ply Frangipani guernsey yarn on 2.25mm needles with 8stsx12rows to one sq inch.
I have presumed that the yarn still retains some oil as it hasn't been washed yet and it certainly smells really woolly. Nice!
Results below.

The water has pooled nicely into a shape rather reminiscent of one of the old maps of the island, when it was known as "Garnsey" in England

Three minutes later after pouring off the surplus and it's looking quite wet, but what does it look like on the inside?

The inside of the guernsey, photo taken immediately after the second picture.
Yay! It's clearly still dry inside, so guernseys really must have amazing water repellent qualities.

Ah, but wait; in order to get a proper result, I must do the test again I reckon. So a second lot of water is poured onto another part of this sleeve.

Here it is after two minutes, having pooled into another interesting shape. 

Next, I pour off the excess water and do something almost unheard of in such tests... I put the sleeve on! 

Then I do something even more unbelievable and actually bend my arm. You have to understand here that I am only trying to replicate what a person might do in a real life situation.....

Now see below what has happened after I take it off again and turn it inside out. 

Nooooooo!!! It's actually wet inside and my cotton sleeve underneath is also decidedly damp

This wasn't supposed to happen. Oh dear! With hindsight, I'm pretty certain that where I went wrong was to put the item on and then actually dare to move while wearing it.

Back to the drawing board then if I ever want to knit something that is even just slightly water repellent let alone waterproof.

Testing over for now.