Dock Project

My husband had a simple plan when he took the dock apart- pull up the top boards that were placed longways on a slope (which sometimes became slippery and hazardous) and cut them in half and lay them down in planks like the end of the dock. Once the boards were pulled up though, we realized that between the termites and wood rot the boards were no longer reusable. Now we're rethinking the plan. If the top wood was bad maybe it's time to replace the whole dock. I'm stoked about it because one side of the dock is beginning to sink and I've been wanting to do something about it. I have some great visions of a multi-level deck that connects to the dock. The only thing I'm worried about is how to build the dock so that it doesn't eventually sink again. I can design and build stuff but I'm no engineer. I don't think either one of us know how to solve that problem. This simple project has turned into a big project that probably won't get finished this year. Maybe?