They seem to have an elaborate process of cleaning and make a bit of a show of it when you return the gear at the dock.
The cheapest way, bleach. I am sure they rinse it but I would do it once again....
With alcohol cleaner (you can taste it)
Your best bet is to bring your own. You should call the captain or crew for that information, but I would imagine that snorkel gear would be at least cleaned with some sort of sanitizers
With water 🙄
Spit
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