Betsy and I have been observing splash-dunks and spin-drys for the last few years. To date, we've observed 338 splash-dunk events, which we define as a case where a dragonfly (usually a darner) plunges into the water one or more times to clean itself. When we see an event, we count the number of successive splash-dunks that occur. The total number of splash-dunks we've observed is 780.
The maximum number of splash-dunks observed in a given event is 8 – at least, so far. This particular observation is described in the The Case of the Constipated Darner at the following link:
Here's a histogram of our combined results for 2011, 2012 and 2013:
The average number of splash-dunks per event (2.31) and the least-squares fit to an exponential have changed very little from last year's results. Here's the analysis of the data:
Overall, the drop off in the number of events is roughly exponential, though there appears to be a larger number of three splash-dunk events than one might expect – a bit of a "shoulder" in the data there. We'll see how these results evolve as more data is collected.