See if there's local wifi at the marina. If so then you could add an
antenna to the boat and a wifi router to make the connection to it. I did
this on our boat using a pair of wifi routers. One picks up the signal from
shore (using it's wifi radio) and it's then wired to another router
belowdecks that provides a local 'on boat' wifi network. Works great. All
I have to do when making port is pull up the shore-link router's config page
and select the appropriate wireless network from shore.

Otherwise you're faced with the hassles of using cellular company network
cards. They do work if there's coverage but they're not cheap per month.
Satellite based stuff is generally not cheap, nor for the units themselves
nor the monthly service fees.