If you ever run out of space to build, you'll just make space like in the Netherlands. Sadly there is no tool for this in CXL (yet), but I found a way to do it. Three tutorials:
This tutorial contains a mod not compatable with CXL 2011 and the problems within could be solved by a different mod (it's in the tutorial, too).
Beach and island-shapeFirst, build a water road. I used Pharmists water roads. If you want to build the beach right away, you have to make the road higher by pressing SHIFT and move your mouse.
(The problems further in this tutorial could be solved with the OWP buildings) Then, add the house you see here (America pack, residences) twice and as close to each other as possible if you want to place a T1 or T2 building. The road has to be straight where you want to build your building.
Add this one twice to add a T3 building (America pack, buildings).
You can do this as many times as you want and when you think your island is complete, you can add the scenery (I'm lazy so I don't build a whole island), I used Nicko2u's wooded forest area, but you can also use other plaza's which can be built over water. Then delete the buildings.
Place the buildings you wanted to place (you have to have a mod to build buildings on water, I used qwertyuiop123's one..
As you see it perfectly fits: you see no water and there are no trees in the buildings.
If you'd just place the buildings you want to place and then add the scenery, it'd look like this:
To make an island with a beach, you have to make the boundary of the whole island first using Pharmists water roads again. Don't make the road higher than it is. You will delete this road later so it is not important which one you use.
Then you have to make the boundary of the island without the beach, choose carefully: this road will stay. This road has to be higher than the previous road. You can adjust the hight of the road by pressing SHIFT and move the mouse.
Then you have to make the beach between the roads. I used Nicko's water areas: the yellow ones more look like sand. Again you can use any plaza you can build over water.
Use the tips in the fist part to place the houses on the island.
Delete the outer road.
Harbor and a partial beach
You can't build a normal harbor in the water when it's not partially on land. There is only one harbor that can be (for as far as I know. If you know another one, leave a comment) and that's the one ofNEXL.
Place a water road, but make it higher by pressing SHIFT and moving the mouse. It has to be just above the harbor's road, otherwise you'll have a wall at the road. It'll say it's an incomplete bridge, so just make a sharp turn so that you can delete that.
You see: it's completely flat.
It looks better if you make the rest of the island a bit higher than the harbor.
Make your island complete with the techniques you learnt in this tutorial.
To make a beach with an end, use the water roads again. Make any shape you want (not this one for sure ), but be sure the road doesn't connect to the existing road.
Fill it up with the sand I used in 'Beach and island shape' (it's water but it looks like sand) and delete it.