There are some 10 million seagoing vessels of all sizes that are capable of carrying a GPS and depth sounder. If even 1% of these logged data, it would go a long way to filling the data gap in may areas. Most of these vessels are small craft, whose depth sounder works to about 100m, so these are relevant for coastal waters. Offshore there are under 100,000 vessels in all - ships' echo sounders will work to about 2000km depth, whereas only a few hundred research vessels and deep sea fishing vessels will be able to plumb deeper depths.
The data that can be produced is not as good as a professional multibeam survey, but is significantly better in accuracy and coverage than a lead line or early echo sounder survey, and is on a par with newer methods such as optical satellite derived bathymetry, but with a greater depth range. To get the required accuracy we need many tracks covering an area, ideally from a number of boats, so that the inherent inaccuracies can be dealt with statistically. Also, to cover as many waters as possible, we need to recruit a wide range of vessel types, as each has their own habitat, sailing in specific parts of the oceans.
The data is perfectly adequate for creating a baseline bathymetry that fills the data gap and is good enough for many applications. In critical areas, such as where safety of shipping is involved (with ships often working to under keel clearances of a few centimeters), or for detailed plans for offshore engineering, crowd sourced data can be used as a pre-survey tool to better target the use of a multi-beam survey of the area, which should always be seen as the gold standard of current survey techniques, but also the most expensive by far.