Comment 0 for bug 1505345

While working on water-like terrains which are impassable for ships (bug 951554) but should be passable for the widelands residents (see https://wl.widelands.org/forum/post/14881/ ) there is a need for a new "is" value. This is because we have "dry" which means impassable by boats, not arable, but passable by roads so it fits likely. But if we use "dry" critters could walk on them too and this looks very disturbing.

The new value, f.e. "shallow", should have following properties:
1. impassable for ships
2. impassable for onshore critters
3. passable for widelands residents (see below)
4. not arable
5. valid resources: fish

For the third property we also should implement a new type of road: footbridge. Otherwise we will have muddy roads over shallow water... i worked already on such a road image, but its not completed yet.