I went off road with my truck last weekend and did some 4 wheeling. We had to cross a couple little streams during the adventure. I thought I heard them sizzle as I entered the water? What could have happened to make them shake a little while braking now?
Your brake rotors may have been extremely hot and going thru the water has warped them so you get the pulsation you feel now. If they are thick enough they can be turned down but you should put new pads on as well.