hi !
large water offen have names - but they did noch have define borders because they are parts of the coast, a sea or the name waterpart will be diffine by costlines and islands. (example north sea, baltic sea, english channel, …)
did anybody have a idea - your opinion ??
reagards Jan 
Waters, mountains, valleys and similar big features don’t have names. I found some proposed features about mountains, but none are used yet.
Hi,
not sure that I fully understand the question. As I understand it well, the water area in the harbour of Amsterdam is a point in case. Here http://www.openstreetmap.org/?lat=52.41937&lon=4.76023&zoom=15&layers=M you can see how the different parts of the water do have different names.
It requires to separate the different water areas,
if it is the answer to a different question, apologies, Hugo
He means large areas of water like seas and oceans.
Hi,
one step larger can be found here: http://www.openstreetmap.org/?lat=52.6074&lon=5.0764&zoom=14&layers=M Hoornse Hop is part of the larger lake IJsselmeer. If you scroll around on the map in the area, you will find different similar names e.g. Gooimeer (Southern part) . Is there a fundamental issue where at a certain size this does not work anymore? It is annoying though, that the current renderer only shows the name at a zoom level of 14 of more detailed, for areas like the North Sea that is not sensible.