Nice everything underwater you gotta teach me how to do that!

To be able to build your towers wherever you want (including the water), you have to make them Ground-pathable (unit property: Pathing-Placement Requires => Ground-pathable).
But now, players can build towers on the monsters' paths. To prevent this, you have to put regions on every path and then make trigger that removes towers built in those regions and gives back the gold player spent on them.
I hope that helped.

Thanks, but I made a big mistake, I thought you had this whole thing under water. True it is shallow, but I expected deeper. But thanks anyways. Good map 4/5

This is a good beginning. I used every single tower on my three attempts so far, which isn't very common in a tower defense. However, near the end everything I saw had fortified armor, making the speed tower seem like the obvious choice for everything. I'm not sure if this changes though, because I have only made it through a few waves after the Emerald Dragon.

The pirate treasure is interesting but a little simple. All four treasures are the same, and there's really no challenge involved. The only thing I had to watch out for was timing, so that I was able to keep my eye on the waves and still get the gold.

I would suggest randomizing what the treasure is. I haven't actually used the editor in months, so I'm not sure if this works, but I do know there is a random item option in the item pallette. If you could limit the items it draws from to a set (so that it doesn't spawn a Skull of Gul'Dan, or something else useless) you could just put down four of those. If not, there's always triggering.

Some ideas for treasures are placeable towers, items for the worker, you get the idea. Have some fun with it.

After you've refined what you've got, it's time for the really important thing. You need something unique, even if it is only one thing, perhaps even a trivial thing. Something that stands out is always important, even if your tower defense has quality (something that does in and of itself stand out). For example, I remember there being a TD called "Stackers TD" or something similar where the focus of the map was on the fact that you could stack towers on top of each other--no pathing. That one aspect not only interested me enough to download it, but it also was enough to make me play it more than a few times.

And then there are some TDs that go over the top. Skibi Castle TD is a good example of some major, major effort that paid off big time.

You're off to a good start. I'm sorry if this hasn't helped much (I realize I'm being vague) but even though I lack the words, your map excites my interest enough that I just had to let you know. Here's my rating, in a nutshell:

Balance: 4/5

As stated previously, I used every tower available. This is a rarity and a great strength for your map. However, near the end the uniformity of enemy armor types cancelled this out.

Originality: 2/5

This works, in essence, like every other TD. What seperates it is quality and the potential for enhancement.

Bugs/annoyances: 5/5

Nonexistant! Some common mistakes, such as making a splash tower with bash or releasing air waves all at the exact same time, are avoided.

Overall: 3/5

Keep on truckin'.

Thanks LAN Party for great suggestions. I'm working on it.

Map is completely under the water (shallow water).

If you find some writing errors, let me know (English is not my native language, so you'll forgive me if I wrote something wrongly). Any suggestions on improving my map are also welcomed.

Map is updated. I think it's a bit more interesting than previous version. Have fun.

The design, and ideas intrigue me. I guess I will try it out.