I used to be sick with sinusitis every single year(especially winters) for approx. 8 years. I don't even want to count how many packs of antibiotics did I consume during that time.

One September, I started to shower myself with cold water at least once a day.

It's been 4 years now and I haven't taken a single antibiotic since.

It also has a great mental effect - doing something a bit uncomfortable every single day makes it easier to do something else that's also uncomfortable.

Cold showers are a great way to start your day. It takes a while to get used to them but I've always found them refreshing. River immersions, I don't know.

Yeah. Look up “Wim Hof”