I’m also starting to build other water/ground vehicles for underground exploration - communication and localisation are challenging, without speaking about navigation on uncertain terrain. Pi are accessible and cheap, and the Pico’s are also very useful to interface with the motors, sensor and so on.
I happen to drop equipment into the sea for a living on occasion, and we always paint it in garish yellow for visibility and label it clearly with contact info to allay suspicions. Typically "Scientific instrument - flux capacitor, Acme Co. - www.bar.org // foo@bar.org // 555-2368"
Also, we notify the coastal administration and the mapping agency so that an EfS (NOTMAR; Notices for Mariners) may be issued if they deem it necessary.
A cynical colleague suggested we had better label them 'Highly radioactive' to keep fishermen from picking them up and taking them apart out of curiosity...
https://www.theguardian.com/world/2025/jul/11/colombia-narco...