Tower Tech is correct about the marine radios. Although the marine band is licensed by rule in domestic waters (no license is required if operating recreational craft within US territory), those frequencies are only legal for use on water.
The Cobra MR-425LI you mentioned is a solid combo marine/GMRS radio that can be a good solution for both marine and land use, however you do need a license to operate on GMRS frequencies.
CB isn’t bad way to go if you need the radio on road trips when travelling in convoys. CB isn’t where it was in the 70’s, but isn’t really dead and there are still a lot of them out there. Personally I think that’s a plus, because it means the channels aren’t as crowded as they once were, which gives you some breathing room if you need them on the road for communicating in a convoy.
Antennas are not mix and match. It’s almost a science, but the short answer is you need to choose the correct antenna for the correct bands and frequencies and the correct radio (handheld, mobile, base station) as well.
The bottom line is this: radio is primarily a tool for communication. It has its strengths and it has its limitations. The best way to determine the right tool for your specific need is to learn about the differences between these tools and choose the one that you feel best fits your needs within those limitations.
We have a lot of resources on the basics of these radio services that can help you make the best choice for what you need. Here are a few:
The Two Way Radio Show Podcast
TWRS-01 - An Introduction to Consumer Radios
TWRS-10 - Radios on the Road
TWRS-15 - An Introduction to CB Radios
TWRS-16 - An Introduction to Marine Radios
Articles
Two Way Radio Basics
Getting Started with Marine Radios
A Beginner’s Guide to CB Radio
Getting The Most Range From Your Radio
Videos
Radio 101 - The difference between UHF and VHF radios
Radio 101 - The truth about FRS / GMRS two way radio range