I cant imagine being built on piers would make a difference I'm sure those million dollar beach houses built on piers weren't all financed with 2nd mortgages or personal loans.Its sometimes hard to get a mortgage on camps period no matter how it was built.
For camps it is usually easier to get financing from a small local bank or lending place than the big chain places. Recreational camps can be tough to get financing on, terms are usually shorter and rates are higher.
It is usually far better if you can get a home equity line of credit on your house, or refinance it to get the money.
My camp is on piers and I got financing. My biggest pain point was the fact that the only heath source was the wood stove, followed by no running water. Many of the larger banks turned me away because of that. I went with a local credit union and they took care of it.
Don't Tread On Me is what it says and I'll take that to my grave.