I've worn tri specific shorts (less of a chamois to get all soaked in the swim) and a tri tank for up to a half IM distance. I just swim in my tank and shorts and then hop on the bike for the remainder of the race. Everyone is different, of course, so just find what works best for you. Most people can swim and bike in the same outfit w/out a problem. They even make tri swimsuits that have some padding in the right place. I just can't imagine riding my bike in that- oh the chaffing the nose of my saddle would do to the inside of my thighs...let alone the horror riding around in my swimsuit would cause spectators...