Cool.
I've never been able to get on the dock, myself. Under it, yes,
on it, no.
ETA: Okay, so I just messed with it again and I could not get on it if I just glitched a wall from inside. If I glitched a wall from the outside, though, then went across the island (ending up inside with it all empty and such), I was able to glitch another wall, and then get to it. I swam over to the cave part, and then did have to jump from the cave to the dock; the first time I tried I fell through when I just walked across. I saved a bunch of pics
here, of attempts from inside and outside.