A motion-activated squirt gun is a fun way to keep seagulls away. Most devices of this kind use infrared beam between the sender and receiver.
When the infrared is obstructed, the receiver – which also acts as the blaster – shoots a small amount of water to hit a perching bird.
However, the system only works when the infrared is aligned, so you need to mount both the receiver and sender carefully.
The keyword here is “fun” as it covers only a straight line in a short distance.
We do not promise 100% success rate with this one however it can be an incredibly fun activity to install with children and witness the birds get a surprise!