The channel numbers are rather misleading as the higher ones, introduced when better technology enabled one conversation to use lower bandwidth so you could fit more channels into the same amount of the radio spectrum, interleave the lower ones.
Some of the allocations therefore seem even more arbitrary than they are if you don't see the channels laid out in order of frequency rather than channel number. OFCOM list of marine frequencies website, among others, lists them by frequency, which makes it easier to understand and probably to remember.