There are technical problems using anything above about 50 Mhz on the canal. Ditch crawling by nature is very difficult to maintain communication so the lower the frequency and by that the increase of wavelength will help continuous communication. Therefore the old CB band is very useful for inter-boat communications. As a qualified amateur, I would use 28 mhz as would Keeping Up.
So for reliable boat communications over distance, use a CB band. For close Boat to Boat coms, VHF is the only way to go. This is also a requirement.i