I am ready to buy a VHF marine radio. I am fairly confident about using a radio and I am not looking for an entry level radio. It looks like GPS is common, but do we benefit from things like AIS and MMSI in sea kayaks? As far a brands, it looks like Cobra is the least expensive with Standard in the middle and Icom as the most expensive. I have other Icom radios and they are in a different class than less expensive radios so I am partial to that option. But, other companies may have more experience in the marine environment and offer better features for on the water. Finally, what are the rules about communicating from the shore to kayakers out on the water?

Not really sure about the legality. If you keep your kayak to shore talk on the appropriate "non-commercial" channels like 68, 69 or 71, don't yap incessantly about unimportant stuff and maybe minimize how much you are revealing that one of the stations is ashore, I doubt the FCC is going to come looking for you.

https://bifc.org/US%20VHF%20Channel%20Regs.html

For everyday use, I prefer the Standard Horizon HX300. Waterproof, floats, USB chargeable (no exposed metal for charging in cradles and good for camping, AA battery capable, smaller form, easy to use, large screen.

I also have the HX870 (new version is the HX890) which adds built-in GPS the MMSI for the MOB and DSC feature. The radio is larger and smaller screen/buttons can make it more challenging to use. For trips like crossing Rosario, where it could be harder to provide location if needed, I'd carry the 870.

Shore contact...the radios are technically required to be used on water. I would limit shore to kayak communication to a minimum and only as needed.