From OpenStreetMap Wiki
Tag historic=ship can be used for anchors or other parts of historic ships?
The rendering support for (historic) ships tagged according to the recommendations in the wiki is quite poor.
- In a river: None of the featured layers on osm.org show the ships. Examples:
- In the sea, Mapnik is the only layer where ships appear (but in a quite ugly colour). Example:
- Surrounded by natural=water: this seems to be the only case where all the layers actually show the ships. Example: