Bar 30 Depth Sensor - Offset-official/Nautilus-One GitHub Wiki

The Bar30 Depth/Pressure Sensor from Blue Robotics is an excellent depth sensor, with a maximum depth of 300 meters and a resolution of 2mm. It's connected via I2C to the Pixhawk, which makes it relatively straightforward to do. All that you need to do is place the Bar30 on its place on the end cap, and then connect it to the Pixhawk, in the I2C Port.

This picture shows the Bar30 from the exterior, where it is screwed into the enclosure back plate much like a penetrator.

This picture shows the Pixhawk, where the Bar30 is plugged into the I2C port.

As far as connection, the provided cable likely will work. If you need to extend or re-wire it for some reason, the connector is a Molex 4-pin UART connector. The depth sensor could also be connected to the Raspberry Pi, if that was desired, but you would need to figure out the configuration with the Pixhawk.