Boats do not go over a curve, you can not see an unlimited distance through atmosphere. Water does not curve and boats do not go over a curve. Everything has a vanishing point.
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https://www.youtube.com/watch?v=mZcXOwH7Qa4
I took a picture of the moon every 10 minutes from 3pm to 10:30pm central time and strung them together in a time lapse.
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https://www.youtube.com/watch?v=haS3bewe7y8