Repeat Performance

And Sunday's mystery blip is solved as well.   
My dear friend Chuck offered a most logical and satisfactory explanation for what this fellow is doing and why: taking water samples, of course.  He probably works for the local water district and is collecting data from the lake.  "My" little estuary runs off Lake Whatcom which is the water source for pretty much all of Bellingham.  Now I wonder why that didn't occur to me.  Obviously, I'm not nearly as smart as Chuck. 
 Another mystery solved.