Hey, @God_Zeal, I am the creator of Tower Defenders.
Cool question my dude, and thank you for the compliment!
The water was created using the terrain tool then it was hidden underneath the mesh terrain.
The properties of the water give it the semi-realistic look. Which are listed below;
WaterSpeed = 25
WaterTransparency = 1
WaterReflectance = .05
WaterSize = .05
WaterColor = 131, 165, 164
Lighting and the Skybox can also affect the look of the water, tweak around with those settings and you’ll find a beautiful replication I’m sure.
I hope this helped, good luck!