Advice for building a dock?

[Armueller2001]

Well I'm going to build a dock on our lake and we're probably going to do a 5 or 6 ft wide, 15 ft long one that is stationary, held up out of the water with poles.

I had a couple of questions though

1) What type of wood is safe to use that will not have chemicals leaching out into the water? I guess we could use untreated wood and just coat it with a few coats of polyurethane, any other options?

2) How would we attach the dock to the cement slabs that we want it to butt up against?

Thanks much, if you can offer any other advice please do.