Most scooters are decently heavy, maybe 40-50 lbs. Carrying one some distance to a river while it beeps at you probably takes enough effort to deter casual hooligans.
Our downtown has a pretty extensive riverfront connected to the sidewalk system, it's trivially easy to ride a scooter right up to the river, lift it over a 3 foot guard rail, and pitch it into the river!
The downtown of a lot of cities has bridges over rivers that would be trivial to huck those e-scooters into.