How deep can you get a sunburn?

[WeRtheOcean]

We know that snorkelers at and near the surface can get sunburned. That got me thinking. If the red light wavelengths attenuate first (actually, probably the infrared, if it fits the same pattern), and the rest of the spectrum drops out, in order, with increasing depth, until the blue end of the spectrum is last -- well, if the pattern holds beyond visible light, wouldn't that mean that UV continues down even deeper than the last visible light? Could one get sunburned down there?

Obviously not a concern if one is wearing a full-length wetsuit and hood; but depending on the water temperature, people do sometimes wear a shorty down into those dimly lit zones, and I suppose it is within the realm of possibility that someone might go down in just a swimsuit, too.

 

[Esprise Me]

Can you get sunburnt underwater?

UV-B, the frequency range of ultra-violet light that causes sunburn, is absorbed by water but you need a few metres of it to provide adequate protection. Half a metre of water will still let 40 per cent of the UV-B through...

So no, you really can't get sunburned below where the visible light stops.

 

[WeRtheOcean]

Sure would have been nice if that article had said at what depth the risk stops. "A few meters" is rather vague.

 

[Esprise Me]

The risk doesn't stop at a specific depth, just like the risk doesn't magically start after a certain amount of time. According to the article, half a meter of water will absorb 60% of UV-B rays. For me, that's probably enough that I could avoid sunburn at that depth even with indefinite exposure. For those fair-skinned folks who manage to fry in less than an hour on a cloudy day, maybe half a meter isn't enough protection. But if a mere half meter absorbs the majority of UV-B rays, one could infer that no one really needs to be concerned about getting burned at ordinary scuba diving depths.

 

[Seaweed Doc]

The risk doesn't stop at a specific depth, just like the risk doesn't magically start after a certain amount of time. According to the article, half a meter of water will absorb 60% of UV-B rays. For me, that's probably enough that I could avoid sunburn at that depth even with indefinite exposure. For those fair-skinned folks who manage to fry in less than an hour on a cloudy day, maybe half a meter isn't enough protection. But if a mere half meter absorbs the majority of UV-B rays, one could infer that no one really needs to be concerned about getting burned at ordinary scuba diving depths.

Water clarity also matters. It'll be deeper in the Bahamas than in Puget Sound.

 

[CuriousRambler]

I saw the title and thought "probably not much past your skin..."

 

[WeRtheOcean]

I saw the title and thought "probably not much past your skin..."

Ah, but if that was what I meant, I would have added an "-ly." As in, "How deeply can you get sunburned?"