My reference to cost was essentially as described by OutofOffice, that the boat does not go out at all for that trip so their cost during that time is less than if they ran the trip. However, as also pointed out, the cost of not going out is not zero and far from it. The passenger has a good reason for not going, and for some places, that decision has been made for them by the transport and government, but the boat company is equally dealing with an unprecedented problem that isn't their fault either.
The point of my previous comment, which wasn't stated well, was that there has to be happy medium somewhere between their keeping all the money and delivering no trip and giving all the money back. Both extremes of that screw somebody for a fault not their own.
However, an additional issue is wrapped up in this and that is the apparent fragile nature of these boat charters and our vested interest in keeping them afloat, pardon the pun. Essentially all businesses are under attack right now but even in good times, boat charters apparently have a tough time being profitable enough. (After years of hearing this, I would be so interested in some real numbers on costs vs revenue) Seems like the most used phrase at Aggressor must be "good for one year". That alone makes it very clear that indeed money from the future charters is paying for today's expenses. It's no revelation to say that can't be sustainable. It just gets blurry about where the line should be drawn for what should be the customers responsibility and what should be the business' responsibility.