yes they do where did you get that idea? have you ever been on top of a cliff a witnessed this yourself?
I can't find it now, but there was a thread on this forum a while back demonstrating the sinking ship effect. The poster, a Round Earther, took pictures of a half-sunken ship and then went up on a hill and restored it. He did not see half-sunken ships from the hill.
This was why in my example of a vantage point of 60 feet I guesstimated the horizon to be 10 miles away. It's well known that for an average height person standing with their feet at sea level, it's only about 2.5 miles. I haven't seen this other thread you're referring to Tom, but I can tell without having read it that the point of it would not have been to say that the sinking ship effect disappears entirely, merely that it is altitude related, which makes total sense from both flat and round earth theories.
If the ship had been the same distance away as the horizon, he'd see a half sunken ship.
Tausami completely neglects my post regarding the "inverse sunken ship" effect and also regarding the diminishment of the viewed size of swells with perspective.
Hadn't read it at the time of posting. I'll check it out now and edit this post with my response.
EDIT: As I said in my post, the Sinking Ship Effect works even with six inch swells. Out of laziness I'll try to explain this without getting into the math. Basically, if a ship is far enough away that due to perspective it appears to be half the height of your thumb, then the swells needed to cover it will need to be the same size according to your eyes. Actually, since you're looking down at them on an angle, they'll actually need to be a lot bigger if the swell or wave is near the shore. A random approximation via mental visualization tells me that they'd have to appear to be at least three times that the ship appears to be able to cover it. This number, which I'll call T, gets smaller as the swell in question becomes smaller away from the observer and closer to the ship. Therefore, T varies inversely with distance and therefore with perceived height (how big it looks to your eye, which we'll call P). So aD=PT where a is an unknown constant.
Basically what this is getting at is that while the swell appears to get smaller, how large it has to appear to be also gets smaller so it shouldn't matter hugely.
You are incorrect with this. Probably because you are using "a random approximation via mental visualisation" rather than maths. Also, the sentence "they'd have to appear to be at least three times that the ship appears to be able to cover it" does not make grammatical sense as far as I can tell.
You also ignore another crucial aspect of what is needed in order for a small object to block the view of a larger one. If we take the situation of a flat plane, as Tausami claims the earth to be, let us call the height of the observer's eyes H1, the total height of the object needing to be obscured H2 (the ship) and the height of the top edge of the small object doing the obscuring H3 (the wave swell).
In order for a smaller object to completely block the larger one
at any distance, H3 must equal or exceed H1. You can hold up a tiny coin and block the view of a huge building, but even right in front of your face, the height of the top of the coin must be at least level with your eyeline. If it isn't, light rays from the large object can travel all the way to your eyes. If you don't believe me, draw a diagram.
The consequence of this is that if you're just 10 feet above sea level, and you're looking out at a ship thirty feet tall, no matter how far away it gets, you'd still need a wave swell of 10 feet minimum to cover it. If your elevation increases to 60 feet, you need a 60 foot swell, and so on.
An analogy would be imagine you're standing on a flat field watching President Obama giving a speech at the other end of it. He's on a podium which raises the height of his head to 10 feet above the ground. If you're right at the back of the crowd, and standing on a box that raises your head to 12 feet above the ground, then no matter how many people are in the crowd or how big it is, if all the people in it are six feet tall you'll still be able to see President Obama.