Underwater messaging made possible by smartphone app

AquaApp is the first mobile app for messaging underwater that works on existing smartphones. Image: University of Washington

A smartphone messaging app for snorklers and scuba divers has been developed by US researchers, making underwater communication accessible "to the masses”.

For those who enjoy snorkelling and scuba diving, hand signals are the only option for communicating safely underwater. Professional divers’ vocabulary can exceed 200 signals on topics ranging from oxygen level to the proximity of aquatic species.

The visual nature of these hand signals limits their effectiveness at distance and in low visibility. Now, for the first time, researchers at the University of Washington have found a way to deliver underwater messaging via smartphones and smartwatches using only software.

AquaApp is the first mobile app for acoustic-based communication and networking underwater that can be used with existing devices.

Image: University of Washington

Co-lead author Tuochao Chen, a PhD student at the Allen School of Computer Science and Engineering, 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.”

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

Shyam Gollakota, Allen School

The AquaApp interface enables users to select from a list of 240 pre-set messages that correspond to hand signals employed by professional divers, with the 20 most common signals prominently displayed for easy access.

In building the app, Chen and his collaborators, fellow PhD student Justin Chan and professor Shyam Gollakota had to overcome technical challenges that they hadn't encountered on dry land.

Chan explained: “The underwater scenario surfaces new problems compared to applications over the air. For example, fluctuations in signal strength are aggravated due to reflections from the surface, floor and coastline.

“Further, microphones and speakers have different characteristics across smartphone models. We had to adapt in real-time to these and other factors to ensure AquaApp would work under real-world conditions.”

The team tested the system in six locations offering a variety of water conditions and activity levels. They evaluated AquaApp’s performance at distances up to 113 metres and depths up to 12 meters.

“Based on our experiments, up to 30 meters is the ideal range for sending and receiving messages underwater, and 100 meters for transmitting SoS beacons,” Chen said. “These capabilities should be sufficient for most recreational and professional scenarios.”

The app reduced the devices’ battery power by just 32% over the course of four hours, which is within the maximum recommended dive time for recreational scuba diving.

Gollakota said: “AquaApp brings underwater communication to the masses. The state of underwater networking today is similar to ARPANET, the precursor of the internet, in the 1970s, where only a select few had access to the internet.

"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 team’s data and open-source Android code are available on the AquaApp website.