How do I build a foot bridge over water on a budget?

I purchased a 6 acre lake last week that I cannot walk all of the way around. I need to build about a 150' bridge over the shallow end which is 2' deep when the water is up.
I do not have a huge budget but could afford a few workers and $1,500. I plan on using those posts from the Hardware store that are 8' long, round with 2 flat sides, and may be made of cypress. The ground is very soft and some is under about 1 foot of water now. If you push a stick in the mud it will penetrate 20' before getting firm. Do I just drive the posts in or do I have to put down a pipe, pump out the water, and then put in conctrete as a base? This need to last a long time and needs to be able to support the occational four-wheeler. Please advise.

Hmmm

I think you should buy a premade bridge and just install it. They aren't that expensive.

You should try to find a bridge that is very easily assembled and only a few tools required. Number and label each board, each post and rail and you just match the numbers and put in the screws and tighten.