Our forum hosts at buytwowayradios.com have a great selection of good quality FRS radios and amateur (Ham) radios at reasonable prices.
Rules have recently changed to access more licence-free channels on FRS radios. What used to be FRS and GMRS radios combined are now considered just FRS, as long as the output power is under 2 watts (which most consumer GMRS radios were anyway.)
I think you want professional-looking but very simple to operate radios that transmit on legal bands and can reach 2 miles across the ocean. Maybe get a couple of good waterproof FRS radios for the paddleboards, plus one higher output amateur radio for the shore station. (Surf shop.)
It is not legal to use that amateur radio on FRS, GMRS, MURS or marine band channels except in an emergency, but there is nothing that says you can’t monitor (listen only) on the surf shop radio. But you now also have the ability to call the Coast Guard in an emergency, and they are not going to be concerned about licences until after everyone is safe.
With FRS on the paddleboards and one amateur radio in the surf shop, boarders can’t accidentally call on the marine frequency, which will really raise Coast Guard attention if it is not an emergency. Technically, you cannot use an amateur radio to transmit on FRS or GMRS either, and no one on these forums is going to advise you to do anything illegal, but lots of people have programmed handheld amateur radios for FRS and GMRS frequencies, and I doubt anyone will know or care.
You might look specifically at the new Baofeng UV-6R. It is water resistant (NOT waterproof) but if it’s inside a waterproof pouch, it will be fine. Plus, it has very good audio, which will help it be more readable from inside a plastic pouch. Plus, at $29, if it falls overboard, no big deal. It is an amateur radio and can’t be used legally on the FRS frequencies, but lots of people have. It is easy to program yourself with the software and a good cable. (Get a GOOD cable, with a genuine FTDI chip, not some cheap clone cable, and it will save you a LOT of heartache!)