Well, I have been to the coast in the past, along Queensland's south coast, NSW's coast in various places, Victoria's Great Ocean Road and other locations, and the WA coast. A couple of things I noticed on those trips: increasing altitude brought more things into view, the higher you went the more you could see, like the oil/gas rigs in Bass Strait; and container ships anchored near Newcastle went from appearing to be below the horizon when close to shore, to sitting on the horizon, to being progressively hidden by it when they passed further away (this on a pretty calm sea too).
One point there I'd like to expand on: from a high-ish vantage point, the ships appeared to be traveling up a hill, cresting it, then going down the far side. On a flat earth, this would not ever be the case: the ships would have appeared to shrink as they drew closer to the horizon, eventually becoming impossible to see (without magnification), without ever having "gone over the hill"! This is because, on a flat earth, the ships being below eye level would always be below eye level, and the horizon being at eye level, would therefore always be above the ship.
Make sense?
I was only asking you to do these photos if you could because I never did any when I was there (it was some time ago), and I also wanted to see if you could show me (and everyone else, of course!) the exact phenomenon you are talking about.