A nice healthy atmosphere could mitigate some of that and extremophiles could, possibly, endure it without a heavy atmosphere. But life, if it's there, is probably going to be weirder than weird. The fact scientists are still talking about possible life on Titan tells me that well-adapted forms of life may very well be able to handle anything Proxima b throws at them!
7cm of fresh water has a ionizing radiation protection factor of 2 meaning it halves the dose of ionizing radiation of which xrays and gamma rays are. The surface dose of earth for all radiation is on average .000001 R/hour (1 mSv/hr) 100 times this while high by human standards would be none existent under 1 meter of water. To put this in perspective fresh nuclear reactor waste is stored under cooling pools that you can walk up to the edge and see the blue glow of the water perfectly safe. fresh reactor wastes has a 100000 R/hour rate lethal to humans in under 5 min yet under 2 meters of fresh or salty water which has a higher radiation absorption rate due to greater density humans can walk up to the edge of the pol and view the waste. while the surface radiation may be lethal to higher lifeforms under a few meters of water that radiation is attenuated and life would thrive visible light penetrates 10000 of thousands times further that high energy photons due to water’s molecular structure being near the wavelength of gamma and xrays causing massive scattering in the first few cms.