How long Bluetooth 4.0 works under the water

Many times in the internet people were discussing that Bluetooth does not work under the water or should work with very small distance. Radio waves cannot go through the water and etc. But nobody tells exactly how log it works underwater.

I made exact experiment and found what is the maximum distansce. I took bluetooth smart (ANT+) heart rate monitor (MIO Link), multisportwatch Garmin Fenix 3, smartphone Sony Xperia Z5 in waterproof case and a ruler.

I switched on MIO Link, get HR signal on both Fenix 3 and Sony Z5 on the air. When I put it underwater and check how it works with 5 cm (around 2 inches). Everything worked fine. I got heart rate from MIO Link on both smartphone and sportwatch. Then I increased distance to 10 cm (around 4 inches) and check it again. Fenix 3 was fine, xPeria Z5 not so good. More than 10 cm nothing works stable.

I recorded my experiment here:

Final conclusion:
Bluetooth LE (low energy) or Bluetooth 4.0 works under the water fine up to 10 cm (4 inches). ANT+ protocol works for the same distance.

You can find this post interesting if you search something like this
"Underwater Bluetooth"
or this
"does bluetooth work underwater"