Anyone who would happen to come across it is likely to be suspicious of its origin and purpose, though. I happen to drop equipment into the sea for a living on

Anyone who would happen to come across it is likely to be suspicious of its origin and purpose, though. 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...