Use a wading staff for additional support. I like the Simms Rivertek wading sandals, might give them a try. As far as indicators go, I like and highly endorse the "Thingamabobber" available at most fly shops. Available in four sizes and various colors - even glow-in-the-dark - I like the white and use the small size glow-in-the-dark on spooky water during the day due to its smokey/dun color.
I don't use mosquito repellant.
Good luck, but if nothing else, make sure you use the wading staff for extra support while you wade.

Kelly.