How to build a pool tunnel and cave?

Question

In my pool, at the deep end, theres a place on the side where it's like a bench on the side so you can sit in the deep end. I was thinking I want to make a cave there so it's kind of secluded so you'd swim there into a cave. I also want to make a tunnel underwater that goes along the side of the deepend so you have to swim underwater to it. (I saw something similar on tv in someone's pool. What type of matieral would be best I was thinking brick and make it go around as the cave and down but don't know if that's the easiest then using something to make the tunnel. Anyone have any ideas? It needs to be as cost effective as possible but yet look decent. Here's a picture of the area I'm doing it at.

http://img168.imageshack.us/img168/9082/n48507056319159307318yw4.jpg

so make a cave outside the water on 4 sides and the side thats over the water go down farther like 5 feet as the beginning of the entrance and put sides on the side of that so it's a box against the pool.

Answer 1

concrete is what most people use. This is going to be a huge job...and i dont think its wise for you to do it yourself. But you can try!!

You need like a mold first,, and then get a lot of concreat and start molding!!

Concrete is really a big mess so it would be wise to get osmeone else to do this for you...