Nautical maps (available, but not the default on vesselfinder) are usually a bit special. There's custom standards like ENC s-52/63/57 etc. Typically with a hug

Nautical maps (available, but not the default on vesselfinder) are usually a bit special. There's custom standards like ENC s-52/63/57 etc. Typically with a huge amount of symbol layers etc. Which is just one of the many reasons they may have gone with a custom openlayers solution