I think this one may be quite close.
Well predicted, Captain. It was a tight match.
Agreed, Dolmot - how did you do that? It looks like a painting or a photograph!
It
is a photograph. Of painted items. That's in the rules.
(I'm here all week.)
OK, seriously... Is it magic? Is it stage magic? Done with mirrors? The possibly surprising revelation is that while people tend to assume trickery, very little is involved here. The correct answer is that it's just a deep setup.
The crucial part is a 130 cm long strip of textured plastic film, intended for window frosting. I've used it before in coastal games and once in an LPL entry. Back then I found the "open sea" view too problematic, thus I settled for a using the quay as a hard edge, but some pig-headed determination made me try the original plan again while expecting different results. However, this second attempt was helped by my recent move to a new apartment, which can accommodate a massive gaming table. Definitely more convenient for building deep scenes (including the far away backdrops and space for the camera) than crawling on the floor.
So, it's no more special than placing the sheet over suitably blue-green t-shirts. Because the sheet was stored rolled up, some large "waves" were already present without any special effort, thus I left them there. The whole setup was lifted a bit (with standard-sized board game boxes) so that I could bend the far end just a little bit down to fade the horizon line. By using f/13.0, no more, no less, I got just enough depth for about 5 cm of sharp focus for the minis while blurring the foreground a bit and the background a lot. This kind of limited depth is often handy for, well, focussing on the entry, but in this case it was even essential. Otherwise the truth about actual depth - large yet finite - would become obvious.
Everything else in the pic is just resin bits and a 40 cm deep harbour piece I had built for games some years go. That's how far away the boat and the shack really are, the latter partially supported by an extra padding piece not visible in the shot. The ripple sheet is just 46 cm wide so I had to adjust the angles quite carefully to have a complete horizon for this frame.
There's only ambient light, combined with ten seconds of exposure to get the flat lighting resembling a late and/or overcast setting.
Unfortunately, I don't have a "making of" shot of this setup. Sometimes I've taken those as well, because the total chaos beginning immediately outside of the frame (and often already between any obstructing pieces) is kind of hilarious. Here it involves board game boxes, t-shirt sleeves, sheet ends held down with random resin pieces, and a warehouse floating halfway on thin air, but when you don't see it, the illusion of an infinite world is strong.
Maybe it is trickery, after all, but so are most TV shows and movie scenes too...