My normal guy will make a quiet little whistle noise if he is nervous.
You really need to get him out of the water bowl and into a tub. If he is just striking out in defense it won't hurt too bad if he gets you.
Open mouth breathing is a distinct sign of an RI, you should listen for any popping/wheezing noises. If you have lids for the tubs just put his in a seperate area.
-Do not medicate your snake with anything until a vet examines it and gives you proper meds!