I live where the ground is mush. We use two kinds of foundations: 1) piles (tree logs) driven into the ground to refusal (usually 100’ - 120’ down), or 2) piles driven until acceptable for friction.
1) Piles driven to refusal are designed to bear on bedrock.
2) Friction piles are designed to resist a load based on the ground “grabbing” onto the side of the pile.
Because it’s so expensive to drive piles, they’re designed to be spaced 20’ - 25’ apart. Then large grade beams (concrete beams) sit on the piles.
Wood piles will rot due to bugs. Bugs can only live with oxygen, which is in the top 10’ (due to tidal action), so we only treat the top 15’. The remaining pile is a “green” tree trunk.
Caissons (concrete piers) are also used, but they are so heavy they often sink under their own weight.
I’d recommend treated wood piles, but you need to know the characteristics of your soil. I’d hire a geotechnical engineer to take soil samples and let you know the best foundation to use.