I'd say it would be Nautilus who would be screwing your agent.
While not suggesting not to dispute, disputing the charge doesn't automatically result in you getting your money back and done. The CC company would consider the purchase, terms, etc to decide whether it is reasonable to refund your money. They owe both sides of the trans a review of the purchase. You might, I mean will still have an uphill battle to get your money through them.
Separately, not allowing people to reschedule doesn't seem to be reasonable since it would allow them to keep your money from the originally scheduled trip really for doing pretty much nothing (i'm thinking that boat maintenance is an ongoing cost that happens regardless)and then having to incur the same cost they would have now but at a future point. Given the reason this happening (all people affected worldwide) it doesn't seem reasonable. However, prior to this event, we've seen some companies feeling that customers perceptions of their companies are not so important.