Needing help understanding how to best setup strong omnidirectional wifi on an international sailboat.

So, long story short I live on a sailboat, and I want a good connection to shore Wifi stations wherever I go. (I'm an Engineer, but WiFi isn't my area at all.)

I saw this antenna: https://www.amazon.com/dp/B0029OQ73E

And this "unit": https://www.amazon.com/dp/B002SYS22E

Which seems to be highly suggested, but I want to understand what exactly they "do". I have no idea what the second device "does" exactly. I presume it's just taking PoE and using it to boost the wifi link. But it also appears to be a full router, which I don't understand the need for in this application.

However could some other "ground station" do this without being installed at the antenna? I would rather not have the bullet device outside and instead have a long antenna cable so there is only one outdoor connection. (IE. my VHF antenna doesn't need the transmitter to be installed at the antenna.)

Thanks!