If the watch is under the end of the suit rather than exposed during the swim, it won't even be noticed. YOu'll turn the sleeve inside out rather than slide your arm out of it so no damage should ensue. My Nike HRM is pretty big and comes out clean.
Thanks for the replies. Makes sense, I guess you really don't "need" to check the watch during the swim. The top half of the suit will be off, anyhow, by time I hit T1 so just check/time split it then.