VHF marine radios have their own band of frequencies which are different than your so called walk-a-round frequencies, family radios.
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Yes, I've been looking at Standard Horizon handhelds this week and on one of the sites I was browsing there was bold letters saying for use on water only, use on land was punishable by $10,000 fine for first offense. I guess it can cause interference with others using that band on land.
A long time ago all VHF marine radios were required to be license by FCC for about 1 hundred buck for 5 years. The FCC has since allowed VHF marine radios to be used on water with out a license for safety reason. All base stations (land) are required to be license.
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