The operator is clearly putting sales before safety, so be cautious, this is probably not the only safety rule they may be breaking.
One really has to wonder what the rest of the world thinks of excessively risk-adverse Westerners who think like this. One could argue that going out at all, going out without mandating all guests wear PFDs while in the water, and/or going out without mandating all guests slather themselves in rashguards, hats, gloves, and sunblock is
putting sales before safety! There is an enormous difference between the offer of a fruity rum drink before/in between snorkles and downing enough booze to become drunk just before trying to tube whitewater/go scuba diving/drive a car on a public road.
A large portion of the world plays by a less anal-retentive, less black and white, less zero tolerance set of "rules" than we do. I doubt that the presence or absence of alcoholic beverages during a snorkel cruise is really the prime marker you want to consider when deciding whether they're safe. Rather: Do reviews talk about the captain/crew failing to control rowdy guests? Who's writing the reviews, families or raging backpacker kids? What information is available about the boat, crew, captain, and equipment? Failing that, call them up and
ask about what you want to know.
First, it is a hard and fast rule that there is no drinking before and during diving. The first beer of the day follows the last dive of the day. No doubt a little beer won't endanger you, but a hazard of drinking is not counting your drinks. The only safe number of drinks is zero.
Why would anyone make such a strident assertion of obviously shaky truth? Is it paternalism, or do you somehow actually believe what you said to be true? Nobody should be diving impaired (any more than narcosis is already impairing them, anyway) and booze does nothing good for one's level of hydration, but what you just said is so far into the realm of fact-independent absolutes that I can't help but laugh.
Am I advocating cracking open a cold one between dives? No, not my cup of tea for reasons that have little to do with whether I'd be sober enough to conduct the next dive. But assuming a long enough SI I wouldn't yell at a buddy who had just one, either. But if you have a beer with lunch
must you skip the night dive several hours later? Of course not.