That is consistent with when you have fibreglass dust on your skin - you don't know it is there until somethig rubs on yoru skin and then it is mega annoying.

You were going to fix that board - did you grind / sand excess glass off and get it on footstraps maybe?

My next guess is Woodies has become primarily a kiting spot and they have soiled the water?

could be jellyfish... maybe you kicked a stinger.

estuaries which are open to the ocean from time to time are breedeing grounds to jellyfish. when they are growing in the early stages they stack like little christmas trees and break off. the smallest are a fresh / brackish type known as hydra and can attach to fabric and easily skin. hydra has become a bit of a general term for small jellies though.
after rain they can be flushed out to the ocean.