I guess a lot would depend on the size of the rocks. And also on what you have to pass over on the way to the area. Probably don't want to cross your septic field if you have one. Small rocks can get buried as long as it's deep enough.
Been reading along on this. Years ago when the canoe bug was hard upon me, I almost bought a new 147. That's about as light as a good canoe gets. Other things took priority and I never got my canoe, but as I'm reading about your mods I keep thinking on how the wood seats are going to add weight...
I'm not so sure that getting the depth perception is all that important for the room sketch. And not all graphics tools are built with that in mind. You may be able to find stock images that you can import, and perhaps edit the face to look the way you want it to.
Good point. Laminate or vinyl can be installed right over the existing floor....unless it is not level and even. Much cheaper to install, and a clean job. But the OP seemed to have a preference for hardwood.
So in the first quote you are buying new wood floor, 3/4" prefinished hickory. Floor gets installed in a day (maybe two).
In the second quote, you are buying a few boards and the rest of the money is for the labor to take sawdust and glue and trowel that into the gaps. Hopefully, sanding and...
Can you see light through the crack?
I might try pre-drilling and setting in a couple of bolts. Go all the way through and put washers on both sides. You could countersink them for a more "finished" look. Do both posts to make it look planned.