Took my spanial to the beach yesterday he swam in the sea... since then he's been sick... salt water I thought... but he is peeing in the house like he has no control

The salt water obviously upset his bowels. Best to give him a bath and remove any excess salt still in his coat.

Something could have irritated his urethra, he could have been stung by a sea creature, there are a few possibilities, your best bet is to get him checked over by a vet. Sudden changes in behavior should always be seen to.