Hey! I was trying to tell about that in my post... As I made the micro-computer (raspberry pi with relays) internals for this project, I touch on that question in this excerpt:
For this I have made a small rest interface which is pretty powerful and fun, as it can trigger a spray of this giant beast. If there are no sprays ordered via the Hive chain, the whale randomly sprays. Additionally... If one of the fast ferries departing from Harlingen harbour to the nearby islands arrive or depart, and sail through a "hotzone" in the harbour, the fountain gets triggered as well.
For the last part it uses a realtime AIS-radio-receiver actually :) Also fun but not Hive related.
I tried to wrap my head around that part, forgive me I'm not familiar with technicals. Can you explain in layman terms how you make it spray? :)