Marine Debris Tracker lets you log every item you pick up, anywhere, with location and category; the data is open and used by researchers and the US National Oceanic and Atmospheric Administration (NOAA) Marine Debris Program. The app was updated in July 2026 and is available for iOS and Android.
Honest caveat: it is only useful if you log consistently, ideally on a fixed stretch at regular intervals.
How to start: debristracker.org/