Crowdsourced bathymetry can be as simple as attaching a data logger to a chart plotter/sounder and storing to a USB stick.
This example shows 2-sec interval depth soundings from a Garmin Echomap UHD 95sv on the vessel ‘Jack 1’ out of Cairns, Australia.
The new CSB data are used to improve 3D depth models for the Great Barrier Reef.

Sounding data from Jack 1