Due the recent question in the help center: http://forum.simutrans.com/index.php?topic=16850.msg160404
I think the interaction of raising/lowering land and water is very counter-intuitive, so I'd like to propose a change.
Currently, if you have a raised shore and lower it, it becomes water. If you have a flat shore and lower it, it becomes a hole in the ground, creating land around it.
This is probably based on the older behaviour, were we had an ocean level and all land lowered to that level became water.
With the new landscape, it would be more intuitive if lowering a raised shore leads to a flat shore, and lowering a flat shore leads to water; and you could only create land from water by raising it.