A couple of Kenmore Air planes departed from Kenmore while I was at Log Boom Park. The conditions were pretty damp and humid (and were about to be joined by pretty heavy downpours of rain!). This meant the departing planes had a good chance of pulling some streamers from the prop tips. Sure enough, when the Otter took off (and it started the takeoff run a little early which helped the shooting angles) the prop was streaming some vapor. The shape of the cone of the tip vortices as they flow across the fuselage was quite interesting.
A little while later (and just before the downpour began), a turbo Beaver came out. It, too, pulled some nice vapor from the prop tips as it accelerated across the water. A bit of a cross wind was apparently coming in (no doubt related to the impending storm) and they got airborne one float at a time. At this point we retreated to the car – but not in time to avoid the rain entirely!