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 ...

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 ...