The story’s called “Hull or High Water” and they’re on the Rotterdam ferry (https://badmachinery.com/comic/2026-03-11/), so by a process of deduction it’s the Hull to Rotterdam ferry; in these benighted Sealink-less times the entertainment options are presumably less expansive but I will note the P&O website is coy about what exactly the “live shows” it touts on that crossing are… https://www.poferries.com/en/onboard#route

(Reading that site and discovering there are meeting spaces for corporate hire on the Hull to Rotterdam ferry has changed my life in a small but measurable way; in what direction is less certain.)