Wendell Waterjet (Patreon)

Months of Planning. 

-Get to know the staff and the regulars. Schedules, patrol patterns, dispositions.
-Establish yourself. You're a good swimmer. Prove that over months. There's supposed to be someone watching at all times, but prey on their negligence. They WILL slip up.
-Check the angles. This late at night, no one's watching. They're sitting at a desk. Pick a spot where they have to stand or move to see.
-Plan for variables. A random person could come in at any time. Pick a day and time where that's least likely to happen. A holiday eve, right before closing time. This factors into your choice of location as well.
-Execute.

Lore: Wendell is, in fact, a very good swimmer, and learned explicitly for this operation...and maybe one other involving a fish. We don't talk about that one.