I saw the 2006 eclipse on the Mediterranean Sea in calm conditions and looking at my video camera imaging, on a standard camera tripod, the Sun moved up and down in the frame about one-quarter of the frame. Ships will usually continue moving slowly forward to improve stabilization, but there will still be some rocking motion.
Even on a ship, in calm conditions, you can successfully shoot at a reasonable focal length, maybe 400 to 600mm. Fred Espenak shot the APOD image on a ship during the April 2023 eclipse https://apod.nasa.go...d/ap230429.html
You should also try to do something wide-angle. (GoPRO)
There is no sense in using a guiding mount on a moving ship.
Make sure you know the captain's course plan (direction) ahead of time. In 2006, we did not. We were all on deck setting up for the eclipse, pointing our gear at the Sun, assuming we were in the path (I did not have GPS with me). In the open sea, with a high-altitude eclipse, it's hard to get your orientation. We had no idea that about 10 minutes before 1st contact the captain was going to turn the ship 180 degrees so as to travel in the direction of the path! So, we all had to change the direction we were pointing.
Getting on the rail is not that crucial because this is a high-altitude eclipse and you will be pointing high in the sky. What is more important is to know the final direction of the ship as explained above.
Whoever is going to be the "eclipse expert" on the cruise and is helping the captain, give them the message to NOT mark C2, Max eclipse, and C3 by sounding the ship's horns! Our captain in 2006 did that and it was the most annoying thing I have ever experienced at an eclipse. It ruined the audio in everyone's videos for that eclipse. I am serious, bring this up with the "eclipse expert" on the cruise.