Since I'm undecided, I am in the process of objectively deciding between the two sides.  I've seen some good points and some very unconvincing arguments from both sides.

Maybe I'll put together a little spreadsheet-like layout of the different arguments on both sides.

Uhm, have you ever heard of waves?

It all depends on how high the periscope is above the water vs. wave conditions (where the observer and target are in relation to one another and with respect the wave conditions).  Since we know nothing about the conditions (height of periscope and the height of waves) ... these pictures prove nothing.  Some of your pictures DO show the bottom of the ship's hull.

Neil, I'm open to proofs of globe earth, as I am currently undecided about this issue, but this is simply not proof of any kind.  I've seen lots of pictures that were purportedly taken from a great distance where the entire craft was still visible when much of it should have disappeared behind earth curvature.  I'm not ruling out that they were faked somehow or doctored or the distance mis-reported.  But I've seen enough of these that I remain open about flat earth.

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So how high above the water do you suppose the periscope is then? 100 feet?
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"Periscope depth" is a standard term for submariners. So there's your answer.
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If the waves are higher than the periscope then you can't get a decent view.
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Does this image show the bottom of the ship's hull?

Ladislaus,
What you have to understand is that flat earthers are not the ones proposing a model.

We are condemning the globe because it doesn't stand on two legs in terms of the science.

This thread makes assertions about the flat earth, which are ridiculous. Although they seem reasonable on the surface. Just because something only slightly seems more reasonable on a globe doesn't prove the globe. The globe has been disproven and doesn't stand up to scrutiny. What you need to do is study these debunks and decide that you don't believe the globe anymore.

With these globe threads, it's all a circular logic to get you to keep believing what you have always believed. Neil is a bully.

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So how high above the water do you suppose the periscope is then? 100 feet?
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"Periscope depth" is a standard term for submariners. So there's your answer.
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If the waves are higher than the periscope then you can't get a decent view.
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Does this image show the bottom of the ship's hull?

Looking at this picture, the water appears to rise as it gets closer to the ship.  To me it looks as if the boat is just on the other side of the crest of a wave ... which would explain why the bottom part of the ship is not visible.  Why, also, is more of the ship's bow visible than the middle and stern?  There appears to be a curvature of the water up towards the middle of the vessel.  Perhaps the water is being displaced upwards further back as the bow of the ship is cutting through the water?  See my point?  If the bottom of the vessel were being hidden merely by the curvature of the earth, I would expect less of the bow to be visible as well.

So I don't know.  I'd want to see pictures and measurements taken scientifically where all the factors are known:  distance between the observer and the target, height of the viewer above sea level, height of the target above sea level ... taking into account wave conditions.

You have to have some idea of a model.  If you KNOW that the earth isn't a globe, then you have to have SOME idea of what it actually is.  I've seen the commonly-used flat earth map for instance (that's a model).  I'm actually exonerating flat earthers if the model cannot currently explain every detail ... because they don't have the scientific apparatus behind them to actually get any precision on the model.  Right now the model is purely speculative.

The idea of a model is based simply on what we see. We see a flat plane and so presume it is always like that.

But mapping is another issue.

The solidity of the firmament is speculation, but could be proven by science. Not by ordinary folks though.

I agree that the model is speculative. but there are questions over the different models, so people flat earthers are entitled to have different opinions. But one thing we are united around is our rejection of the globe.

Neil, I don't know if anybody else will appreciate this video, but I think you'll have fun with it...

i

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The date at the end says MCMXLIII -- 1943.
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That's the year they made pennies out of steel (saving copper for the war), but about a dozen copper pennies were struck by mistake.
Today there are only 4-1943 copper pennies known to exist and they're valued at roughly $200,000 each (two hundred thousand dollars).
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The video shows precise identification of lighthouse beacons based on their flashing timing which is measured by stopwatch.
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Curiously, such stopwatches were not yet invented during WWI.
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So as our equipment gets more precise and sophisticated, better observations can be made.
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This entire video would be nonsense if the earth were "flat" especially for the Cape Charles Light with 740,000 candlepower and 180 ft. in height.
See minute 2. Visibility is given in their tables based on height of the light above sea level, because of earth's curvature.
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Why is such a powerful light not visible far out at sea? Because of the earth's curvature!