GoAlaskaTours is a broker selling the Allen Marine trips. As I've "fired" my own broker this season, I'm not big on the concept of using them at all unless absolutely necessary.
The Keet is a nice boat - well maintained and usually very clean. There is capacity for up to 150 guests, so be prepared for crowds unless it's a lightly booked day. These are the same boats Allen Marine (and the ships' tours) use for Whale Watching in Auke Bay, Icy Strait Point and Sitka.
IMO the larger boats diminish the experience of Tracy Arm a bit, but for many (especially the budget conscious) it's a great way to go.
Happy Alaska Travels!
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