Depends on what you want. I've made a covered bridge over a decent distance over water or a pine tree bridge over a river that was tall enough to allow boats to get under it.

Try to use rocks as anchors for building integrity and if that isn't possible use wood to build water platforms close enough to the ground so that you can raise it up high enough for building on and then simply dismantle the wood scaffolding afterwards.

Pine trees you'd build on raised ground and then you'd need wood / core wood to build across though you have to be a bit careful with spacing of the trees for building integrity otherwise you'd have to use iron reinforced wood.

edit: If you want you can invite me to your world to check it out.