Will a cell booster help you underwater?

File this one under… “we work hard so you don’t have to.” Several years ago I was asked if a cell booster would work underwater. This was around the time that we first started seeing waterproof phones and it was a hot topic.

How I tested it

Not having the benefit of the latest Galaxy phone at the time, I was able to outfit myself with a used Lifeproof case that a friend of mine was willing to lend me. I hoped that would let me get the information I needed.

I figured that the phone probably wouldn’t work well under water, owing to the way that water bends radio waves. You’ve certainly noticed that water bends light differently from air does, because objects in water sometimes look larger or out of alignment. Sometimes you notice little rainbow edges around things, and that’s due to the way the water bends different wavelengths of light. Even if you’ve never given it any thought at all, you have to have noticed that if the surface of the water isn’t still, stuff underwater looks wavy.

All the same things that you see with water also happen with radio waves. So, my expectation was that signal levels would be significantly worse that they were without the water. Now I just needed to test things out.

Luckily, our Southern California offices were experiencing some very temperate weather at that time and I was able to spend some time in a swimming pool. The things I do for you people, seriously.

The results

True to expectations, I saw lower signals from the phone when it was underwater. The good news is I didn’t completely ruin my phone, but I was angling for a new phone at the time so I was OK with the results. I was actually expecting about a 3dB drop in signal, meaning half the signal was lost. What I got was a 11dB drop, meaning over 90% of the signal that was available on dry land was lost to me in the pool. To be fair, some of this may have been due to being below ground level but I couldn’t drain the pool to test that theory. I did put the phone as low as I could without getting it wet and saw no decrease in signal level.

The takeaway here is that unless you have pretty good cell coverage where you are, you won’t get a whole lot of calls while you’re swimming. The question is, would a cell booster help?

Don’t try this at home

Setting up a cell booster outdoors is sort of perilous, because they’re really meant to be used indoors only. Luckily I chose my swimming pool wisely – it was located in an area where cell service outside was only at the “two-bar” level and I thought I could risk it. I set up a cell booster 15′ up on the roof and strung cable out to the pool area, in fact at the edge of the pool. I then stood 8 feet from the cell booster on the deck to see if I could get some sort of reading to tell me the booster worked.

It did. I went from two bars to four, a 23dB increase. So I could say for sure that the booster was doing its job. I gently slipped into the pool (not wanting to get the booster wet) and went down about 4 feet and over about 4 feet, so the phone could still see the booster’s antenna but there was about 8 feet of water between us.

The results were great. Well, not great but very definitive anyway.

Not the news you wanted

Not only did I not get the 23dB gain from the booster, but I actually measured the same signal level that I measured when the booster was off. I turned the booster off and redid the test. That’s the bottom line here. The booster did absolutely nothing for the phone underwater.

I have a theory here. I think the booster’s signal was bouncing off the surface of the water. On the other hand the cell tower’s signal, because it was higher, was going through the water. Things would have been better if I were able to construct something to hold the booster directly over the water. But I couldn’t do that without risking frying it in a freak accident, I would have done that. But I felt it didn’t matter because you’re not going to put a cell booster right over a pool. Maybe you’d put an antenna over one, if it’s an indoor pool but that’s a stretch.

I learned something in my very uncontrolled experiment. It seems that a cell booster will not help you underwater. It doesn’t matter no matter how close you put it to the pool. I suppose that I would rather it worked out the other way. Still, any result is a meaningful result.  I’m glad to have a result I can share.

In the meantime, if you want a cell booster, shop the great selection at Solid Signal.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.