Just went through that process last summer. Actually I tripled the size of the dock I had built some 9 years ago. This worked well for me but I don't know how deep your water is. I waited till the drought had done its damage and only had to work in 4 to 5 feet. We used 4"treated posts that we cut on the ends(that went in the lake) to a point, with a chain saw. We then got in the water with a ladder and a 10lb.sledge and pounded them as far as they would go and then tied them together with cross members. We used 1 x 6 treated for the deck, but if I were doing it again I would use 2 x 6. If you are not getting much wave action, which you probably are not the weight of the deck and crossmembers are enough to hold it in place really well. We have a 4.5" walkway and the dock now is 10 x 30......It was relatively inexpensive, I thought. Spent about $900 on the lumber and about another $500 for my help.....If you have any other questions please don't hesitate to let me know.......good luck
