Version mkgmap-r4901 was committed by gerd on Fri, 13 May 2022 fix bug in code which is used to generate precompSea.zip Tiles with complex coastlines contained ways with tag natural=sea outside of the tile bounds. Not sure if this cause wrong maps, it seems that the downloadable sea-latest.zip on the mkgmap site was created with an older version of mkgmap which doesn't show this bug. http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4901