Having swam (sometimes not voluntarily) in water temperature from 6deg C upwards, No, 16 deg is hypothermia territory. 20deg C is where you started to be able

Having swam (sometimes not voluntarily) in water temperature from 6deg C upwards, No, 16 deg is hypothermia territory. 20deg C is where you started to be able to swim for extended amount of time (i.e. 1 hr). But the water still feels very cold if it's not a sunny day. Wearing swim shirt is usually recommended. 27-28deg C is the temperature of majority of the pools. 30 deg C is about the temperature of water where you can not move and still feel warm.