The house I'm currently working on is having a new dock built. They are using a mini excavator with a flat, vibrating hammer of some kind where the bucket is supposed to be. It's on a pontoon boat. They are using round logs and leaving the ends flat. They line them up, and the excavator drives them into the ground several feet. Then they attach beams across the top, run joists over the beams and then decking, just like building a wood deck.
On another job I saw a group of "good ole boys" build a dock quite differently. They sharpened the ends of the round posts with a chain saw. Then two of them got into one flat bottom row boat, and another two got into another flat bottom boat. They lined up the post between the two boats, and then they all stood up and worked a home made post pounder just like a T post pounder, but a lot bigger. Every one of them where 300 pounds, maybe quite a bit more. They have done this a lot because there was no mistakes, and they all worked together perfectly. They got each post into the ground several feet, maybe three to four feet in places. They probably pout in 50 posts. It was great entertainment to watch while I was working on that house!!!
I'm still not sure how I will build my pond. I've gone back and forth between wood posts or metal posts, or a floating dock. Floating seems like it might be the nicest, but more expensive.