Hey cityfarmer. If your pond has much variation in water depth thruout the year consider this option: If you look at how most docks are built on rivers and especially ocean or bayfronts (subject to tidal fluctuations) you will notice they don't use the awkward cable setups that many marinas use on lakes. The cable/winch setup of course used to extend and retract the floating structure as water levels mandate. Instead they use a setup where the dock has the piers (which are driven in with huge barge delivered pile drivers) actually coming up thru holes in the dock itself. Being as they are floating docks, they then are held in a stationary position except that they can rize and fall with the tides. Kind of a neat trick I think and it stabilizes the structure while allowing for depth adjustment. I have done buisiness with and on occasion worked for the world's largest manufactorer and builder of docks and marinas - the "Atlantic Meeco Corporation" which is based in McAlester Oklahoma. They can provide anything or everything a person could need for materials for dock building such as those huge slabs of styrofoam whick they make at the plant as well as the polypropolene tubs that they put them in before applying the decking (required by law on most lakes now - keeps the nasty little beads from breaking off and getting dispersed in the water.) Also, I know that the silicone wafer/computer chip manufactoring people use a lot of chemicals that must be stored in poly barrels which are of high quality. I've seen them and collected a few from some of the dumpsters at a few sights in the Addison Texas area. just a thought - they'd make great flotation devices. Use stainless hardware if cost allows. If not...be sure NOT to hammer in any galvanized lag bolts when first starting them etc. This will cause the eventual corruption of the galvanize and hasten the corrosion of the bolts. The most incredible decking material I ever saw was a hardwood out of Brasil called "Ipe". It is used on the premier marinas at the fancy-shmancy docks where rich folks keep their boats. Ipe is a very dense wood, other than the curing and drying done at the mill it requires no other treatment and is MARINE GRADE! It is a little hard to work with since it is so heavy and hard. If it is accidentally kicked off the side into the water by the builders it sinks like a rock. It also is hard on saw blades and drill bits...almost like working with steel or something. But man it is pretty and they say will not require any upkeep even on a saltwater dock. I have seen the tree growing in Brasil and it is a nice looking tree with beautiful pink and purple flowers in the top of it. Wish we grew it here in the states( I think a few areas might.)