Homeade Pool Steps?

[Orbit06]

Hi,
I have an in-ground liner pool with no steps - just ladders. My dog swims in the pool a lot, but cannot get out by herself. I can't afford to buy the fancy steps for $350-$600 right now and I don't really need them. I just need one medium-sized step (she's a big dog) so she can get out without my assistance. I bought a new product I thought might work, but it was too flimsy - it was a plastic ramp that you tie to the pool deck. I keep it to save wild animals that fall in the pool, which is good, but not my goal.

I want to make my own step to put in the floor of the pool. I'm wondering what materials are okay for inside a pool, ideas for weight, anything? Any suggestions? Is it a good or bad idea?
Thanks!