Useful but not the ants pants
Pretty good for map and markers but no reliable depth details. OK therefore for sports and recreation use. More serious users would prefer C-map paid version.
Why
For any Great Lakes users it's useless. No data whatever.
Needs more coverage
The OpenSeaMap project appears to only cover some specific areas, but from what I can see where there is data provided it looks great. I look forward to US West coast coverage!!
No information provided
This app provides zero marine information overlay. Only provides a generic land map. No marine information provided