What's this white stuff on my rudder post?

[Kelkara]

There's some white jelly/waxy/slimy stuff accumulating on my rudder post ... what is it? where has it come from? and should I be worried.

my cockpit drains got blocked sometime over winter, and the tarp obviously wasn't keeping all the rain out. so I came back to find the cockpit a foot deep in water. Clearly the cockpit is basically waterproof, but there could have been a slow drip down the rudder post.