For Geonames-ID: 2677368 (Skogsviken) you claim 18 m above sea level. That is very wrong. Maybe you intended 0.18 m ?
I spend a lot of time there and have more than once travelled by small boat between Skogsviken and the Baltic Sea. The difference between the lake and the Baltic Sea varies but is never more than half a meter.
There is actually no elevation stored for Skogsviken. Please feel free to add it: http://www.geonames.org/manual.html The elevation displayed with 'circa 18m' is an approximation of the elevation in the area derived from satellite radar information.