This is the back of the audio module. You can see from top left, clockwise:

1. The surface exciter that vibrates the enclosure to produce sound underwater.

2. The Beetle ESP32-C3 (RISC-V) microcontroller.

3. The BH1750 Lux/Light sensor - TBD.

4. The DFRobot MAX98375 I2S Amplifier module

This is the back of the audio module, from top-right clockwise:

1. The blue solid-state 1 Amp fuse.

2. Adafruit VL53L4CX Time of Flight Sensor - to alert diver if they are too close to the lake/sea-bed.

3. Lithium rechargeable battery (charged through battery charging circuit in the Beetle ESP32-C3)

4. Not visible, buried in the middle! The Adafruit Micro SD Card breakout PCB.