Thanks for the info. I'll go with the treated 6x6s, for only 4 long timbers there won't be a huge cost difference. I can buy one 6' 6x6 timber to cut in two for the two on the shore. I probably don't have much in the way of options for the footers other than putting them "above ground".

I have a design in mind I'm pretty happy with but if you guys have any ideas I'm all ears. I was going to sink the 2 short timbers into the bank, and then the four long 6x6's farther out at the bottom of the slope of the bank in a "square" shape. The two timbers on each side out in the water would be 5'-6' apart. 2x8's would run on the outside of each side and cantilever 3' past the last 6x6 timber on each side. The end would also be finished with a 2x8. I would probably need to run two more 2x8's down the middle to properly support the deck planks. Then 2x4's widely spaced for the planks so rain could run through easily. The benches will be made out of 2x4s or 2x6s in between the 6x6s that are out in the water ... one bench on each side ... facing each other ... a sturdy plank or two behind each on the outside of the 6x6s for a backrest. These backrest planks will be screwed in rather than nailed. I'm plannning to use SS nails throughout, put an aluminum or SS folding swim ladder on the end, and copper or synthetic caps on top of the 6x6s ... going to leave the timbers sticking up high that the benches are between.