I have tried something else.
I thought maybe I can import the water model in IceX. No, it gave an error wrong mdl format and the complete program (that is IceX) disappears from the screen (strange behaviour for such an error).
Then I imported a player to IceX, export it as WMP file and opened it in WED.
When I tried to apply an action to the player, the player has already an action attached to it (same action that is attached to all the items you import and paste to the level in IceX).

When I work The other way around (making a level in IceX, export it as a WMP file and opened it in WED) I can add items like a prefab, but when I run the level that item is not visible at all but it is there because the player can bump into it.

Now some thoughts comes to my mind;
a. is IceX usable in combination with entities of WED
b. are there still some things to be done for the maker of IceX
c. am I doing it completely wrong

Don't misunderstand me, for designing an outdoor level it works like a charm.
But for the rest, I think I give up.

Some advice please,

Regards,
Frits