Most of the whale watchers in Juneau have offered that guarantee at one time or another. I'm fairly certain Allen Marine started that idea, and it was Capt. Larry himself who called it a "fancy marketing gimmick." Orca Enterprises will give you a free seat on another tour if you don't see whales, as will (I think) Harv & Marv. AK Whale Watching offered a partial refund last year if no whales were spotted, and Alaskan Marine Adventures has the slogan "we always guarantee FUN!" (Which, I'm told, means if you want to see whales and don't, they'll stretch the time, go someplace else, get you out on another tour, give money back, etc. if you didn't have a great time.) I believe Adventures In Alaska is the one medium sized company offering a full refund this year... or maybe that's his sea-sickness guarantee...?
Juneau is such a "gathering place" for humpback whales, I honestly don't know how a boat can NOT find them for your viewing! In an entire lifetime, I can only count (on one hand) the number of times I've been out for more than 2 hours and not seen whales around here! They're fully migrated by mid-April, and we've even got a few (17 at my last count) that do not migrate at all.
If it's really early in the season, look for a boat that departs from downtown, or is willing (and has time) to go quite a ways SOUTH of town, down Stephen's Passage. I've often observed the "non-migrators" playing down by Port Snettisham, but most of the whale watching outfits here (all but one) only depart from Auke Bay and don't go to the "South End".
Happy Whale Watching!
Better not for now... signatures get me banned!