It's worth noting that "wet-bulb events" are already with us for people who are not optimally fit. Europe alone has lost tens of thousands of lives due to heat stress in recent heatwaves. Every heat-stress death is a "wet-bulb death" for the person concerned. What the science is still trying to pin down is the practical envelope outside of which no-one can survive indefinitely without active cooling. It is telling that recent news shows that this envelope is not at all clearly defined.

It's also worth noting that water temperatures in some areas, such as Florida, are now into the range where one cannot survive a prolonged period if the humidity is 100%. If you are immersed in water, you also cannot cool by sweating. So from about 32 Celsius upwards you not only cannot cool off with a dip in the sea, you may actually be risking heat stress if you immerse yourself for a period.