Wireless communication between sea-water submerged wearable and esp32 above surface

[dtheodor79]

Hello,

I am working on a project that requires the communication between a wearable (e.g. wristband) that is submerged in shallow sea-water (no more than 30 - 40 cm) and an esp32 that is a slightly above the water surface (about 1 - 2 m). These devices shall exchange few Kbytes / minute. I tried my luck with a first prototype that comprised a Bluetooth-enabled wristband and an esp32, which worked, but not reliably.

So I want to switch to wireless protocols with lower frequencies with the hope of increasing the signal water penetration. I checked that toy RC submarines (e.g. https://aurdel.com/dk/en/gdm-1051) use a band of 27 MHz, whereas other solutions could be LoRa (I am in Europe) or an HC-12 (433 MHz). Although it is easy to find modules for DIY projects with LoRA or HC-12, I cannot find anything that is available for DIY projects based on the 27 MHz band. I could try to buy a submarine and reverse-engineer it, but first I want to know if there is anything available already.

My question is if there are others who have already tried using any of the three above solutions in esp32 projects, under the aforementioned environmental conditions, and eventually any feedback / tips.

Thank you and sorry for the long post.
dtheodor

[powerbroker]

i took part in developing RF I/O from inside of sea cargo container(box of steel) to outside part on surface: inner temperature, banana-gas quality, etc.

we had to add an amplifier chip to CC1101 on 433MHz to keep stable link - the steel box is dropping amplitude about 60 000..80 000 times.

in case of water i would took into account and give a chance to ultrasonic and optical ways - infra-red maybe...

[dtheodor79]

Hello,

Ultrasound could be an option (not sure how cheap it is..), whereas infrared will be kind of constrained, since the underwater esp32 is a worker that is moving, hence the other esp32 that is above the surface would not be able to easily establish a direct line-of-sight.

For sure I will check the cc1101 for enhancing the signal strength

Thanks a lot for the suggestions!
dtheodor79