Lost a GoPro while SUP surfing; it sank. Went back at low tide to see it had washed up in a tide pool! (Lucky there aren't that many people on the beaches in India)
This is the clipped/condensed video of what your GoPro sees if it runs away from home for 7ish hours.
The battery still had juice when it was found, but my memory card was full, I did obtain over 4 hours of footage from the sea floor. I still can't believe I found it!