What can we use for pilings (for a 2700 sq. ft) house for land that hits water at 6 ft?

Such an expense of a new house needs an engineer to determine what foundation is needed. A soils engineer will take bore tests and relay them to the structural engineer. This is a bit pricey, but you would be assured of the best foundation for your house.

My guess is that they would either use a spread footing system, which is a much wider footing combined with steel rebar, or a pile driven system, such as you would see on a boat dock, or cased auger cast system, which would be a series of holes dug very deep, protected by casing from the water and then filled with grout.

Good luck on your new house!

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so you hit water - if the piles are at 6 feet you're below the frost line (depending on where you live) Do you know the allowing bearing pressure of the soil. Why did you go to piles and not a pier footing? I need more info .....

Sounds like the contractor isn't up on things. Here on the ocean they drill down as deep as needed and then they put in a hollow tube (for lack of a better word) they then pour the concrete in the tube. As the concrete goes down the water is forced out. It works here and we are in hurricane ally.

They can drive treated pilings like they do for docks and such, and then build your sub floor on them. They do it for beach houses all the time