I’m also working on making my ROV autonomous.
The first step is to format a SD card with raspian and get ssh working over wifi. You probably want to do this with a separate raspberry pi first since getting an SD card in and out of the blue rov2 is a royal pain. For supplying wall power during development, I used a micro-usb elbow adaptor (80 cents) and a hand soldered assembly which has a male USB A and micro B adaptor connected through a BlueRobotics switch. Sparkfun sells easy to solder USB connectors. The assembly is just long enough to reach out of the enclosure, but short enough to fit inside when not in use. I also found that the sony CP-ELSVP battery fits perfectly in the enclosure, allowing the raspberry pi to be powered without the main battery. I found this useful for test dives.
If you want to record video, use an UHC card. I’m using a lexar 1000x and it works fine. Even so, when you implement your video recorder make sure you buffer everything to memory first and then write it to the SD card. I experienced write latency up to 4 seconds, enough for the camera API to start dropping frames.
If you manage to fit the odroid inside the enclusure, let me know how you did it; I’m still using the raspberry pi. My aim is to navigate using the camera. So far I’ve sped up ORB_SLAM to run at 15 frames per second, but I now have heating issues due to the tight space. Part of the code is published at https://github.com/0xfaded/pislam. The full sped up SLAM will be released soon.