As a surfer on the SB Channel for nearly 40 years now I've done my share of gazing at oil rigs, islands and coastlines N and S. I used to think this kind of view indicated the earth's surface curvature...
...then I started researching these kinds of observations due to comments made in the water regarding seeing things we should not see...because they should be below the horizon. Discovered really quick that we cannot detect surface curvature anywhere. All long distance observations are "as flat". Here's a photo study showing the magnitude of the problem...the horizon is essentially in the wrong place...
These photos are in the Potpourri section...go check them out in larger format if needed.
Many will claim this is due to mirage or refraction. Although these effects do occur...especially at the horizon...they do not explain why we see landscape we should not be able to see at all. Here's a really good video on the subject...even if you don't agree with my conclusion...maybe learn something new....
As stated in another thread, there's photos of landscape up to 300 miles in the distance where the objects seen should be nearly 50,000 ft below the horizon. I've yet to see long range views or images that depict the landscape as if we lived on sphere of nearly 4000 mile radius...it always appears "as flat'. I find this rather intriguing....where's the curvature? I'm still looking....