Researchers have created a messaging app that could make life a whole lot better down where it’s wetter.

Unless you’re regularly trying to contact friends under the sea, you may not be aware that WiFi and Bluetooth signals don’t travel very well through water.

But having a way to send messages could actually be very useful for divers, both recreational and professional.

At the moment, divers tend to communicate with hand gestures. But these are relatively limited, especially when visibility is low.

The ‘AquaApp’ from researchers at the University of Washington have developed could help solve this problem. Instead of relying on radio signals, it uses sound to send information from one device to another.

Co-lead author and University of Washington doctoral student Tuochao Chen said: ‘Smartphones rely on radio signals like WiFi and Bluetooth for wireless communication. Those don’t propagate well underwater, but acoustic signals do.’

‘With AquaApp, we demonstrate underwater messaging using the speaker and microphone widely available on smartphones and watches. Other than downloading an app to their phone, the only thing people will need is a waterproof phone case rated for the depth of their dive.’

The app itself contains 240 pre-written messages that match the hand signals normally used by professionals. The 20 most popular gestures are also displayed on the app’s landing page for easy access.

The team faced a multitude of challenges when building the app to make sure their acoustic signals travelled successfully underwater. They had to factor everything from the way noise bounces off the seabed and surfaces, the ambient subsurface sounds produced by boats and aquatic creatures to the differences in microphone and speaker technology across handsets into their calculations to make sure their signals are strong enough.

The algorithm they created figures out the best kinds of acoustic signal to send, based on the current conditions of a device.

Before actually sending a message, the app shoots a ‘preamble’ to its target device. This triggers the target to run the algorithm and work out the optimal bitrate and acoustic frequency the sender should use to communicate.

This information goes back to the sender’s device, which uses these optimal settings to finally transmit a proper message.

Based on testing, the app works best ‘up to 30 meters for sending and receiving messages underwater, and 100 meters for transmitting SoS beacons,’ co-lead author and doctoral student Justin Chen said. ‘These capabilities should be sufficient for most recreational and professional scenarios.’

Testing also shows it doesn’t drain a phone’s battery life too significantly, using up 32% of the charge of a Samsung Galaxy S9 phone when used for four hours with the volume at max and the screen on.

The fact the app can be used on a normal smartphone, ‘brings underwater communication to the masses,’ said senior study author professor Shyam Gollakota.

‘AquaApp has the potential to change that status quo by democratizing underwater technology and making it as easy as downloading software on your smartphone.’

The research paper was presented at the Association for Computing Machinery’s Special Interest Group on Data Communications 2022 Conference.

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