Here's my thoughts; I may be wrong about some things and if I am, please correct me. Either way, take it with a grain of salt.
From what I have read and heard, the constellation will be able to relay data between the individual satellites. This has been the premise from the get-go as it's been intended that you'd be connected to more than one satellite at a time anyway, so being passed off from one to another is a normal event for even stationary base stations. Even now with the limitations of staying within your cell, the constellation is in motion relative to the antennas, so what would it matter if you added another ten to twenty knots of movement to the equation?
Starlink uses a phased array antenna, and while I have no expertise with the hardware, I was involved to a limited degree with the testing of airbourne phased array weapons guidance and target tracking systems when I was in the military. From what I remember, phased array antennas usually have a useful beam angle range of around 120 degrees and can change the shape and direction of the beam nearly instantly without moving the hardware at all. Based on what memories I have of what I witnessed in the military and what I've read about the Starlink antenna, there's no doubt that it will be able to track and communicate with multiple satellites at the same time while the boat is bobbing around. I also read somewhere a while back that some guy did the math on the geometry of the constellation and when fully populated, the antenna would only have to shift its aim by 10 degrees to switch from one satellite to another.
The thing to keep in mind is that this is still in the testing phase. Beta is the term used when technology has advanced to the point where consumer product testing is required and is the last phase before final rollout. And really, with a project of this scope, there really isn't any other way to test it. Yes, there are limitations imposed now that make it useless for someone beyond cell phone range or with a moving base station, but that's only because they haven't advanced to that phase of testing yet. I'm not a Tesla/Musk fan by any means for many reasons, but I have complete faith that Starlink will indeed provide what has been promised. Consider too that the DoD is funding the project, which is very similar to how GPS came into existence, and there should be no doubt that this thing is on track.
And lastly, the current cost of about $500 for the hardware and $100/month for the subscription is not competitive at all with terrestrial- based internet providers, but it was never intended to compete with or even work in areas where cable and fiber are available. That you will be able to stream a HD movie while uploading to YouTube and making a Zoom call from the middle of the Pacific is phenomenal and at the end of the day, you absolutely cannot put a price on that. Especially when you consider that the telephone connection it will provide also serves as a backup to the radio if things go pear shaped.
