The UAE GCAA released an incident report of a Saudia Airlines Airbus A320 that was damaged at Dubai when water salute went wrong.

Date:20-SEP-2018
Time:c. 10:40 LT
Type: Airbus A320-214 (WL)
Owner/operator:Saudi Arabian Airlines
Registration:HZ-AS55
C/n / msn:7550
Fatalities:Fatalities: 0 / Occupants: 126
Other fatalities:0
Aircraft damage:Minor
Category:Incident
Location:Dubai International Airport (OMDB) –    United Arab Emirates
Phase:Taxi
Nature:International Scheduled Passenger
Departure airport:Jeddah King Abdulaziz International Airport (JED)
Destination airport:Dubai Airport (DXB/OMDB)

Narrative:
On 20 September 2018 at 10:38 local time, Saudia Airlines flight SV566 from Jeddah King Abdulaziz International Airport (OEJN), Saudi Arabia, operated by an Airbus A320-214 aircraft, registration HZ-AS55, landed at Dubai International Airport (OMDB), the United Arab Emirates.
The flight and the landing were uneventful and the aircraft taxied to gate C58 as instructed.
After turning towards the terminal, two firefighting vehicles, which were located on either side of the taxiway, started spraying jets of water to welcome the aircraft with a water salute in celebration of the Saudi Arabia National Day. The vehicle turret operators selected a water jet with a high kinetic energy to form a far-reaching arc.
The fire-fighting vehicle positioned on the left side of the Aircraft, FIRE 8, experienced a problem with the roof turret, which ceased to follow the operator’s input from the hand controller. The high pressure water jet was suddenly sprayed upwards and then downwards, as the aircraft passed underneath. The Aircraft was struck by the water jet causing the left forward over-wing emergency exit hatch to open. The hatch fell into the cabin. This resulted in the deployment of the left over-wing emergency slide ramp.
The flight crew was alerted to the opening of the emergency hatch by the master warning system and stopped the Aircraft immediately. They were not aware that a water salute had been arranged on arrival at the gate and therefore they could not inform the cabin crew or passengers prior to the event.
The aircraft was towed to the gate with the slide ramp attached, where the passengers disembarked normally.

The deployment of the over-wing emergency exit hatch into the cabin slightly injured the passenger seated in the adjacent window seat. The passenger received medical attention and decided to continue their journey after being medically cleared.

Causes:
The Air Accident Investigation Sector determines that the cause of the Incident was the erratic directional movement of the water jet onto
the push panel of the left forward over-wing emergency exit hatch, which, when pushed inwards, resulted in the emergency exit hatch
opening and falling into the cabin, slightly injuring the passenger seated in the window seat.

Contributing Factors to the Incident:
The Air Accident Investigation Sector identifies the following contributing factors to the Incident:
(a) The fire vehicle’s hand controller potentiometer failed to control the movements of the roof turret.
(b) The process of a water salute had not been formally described and risk assessed by the airport fire service, thus the possibility of erratic water turret movement was not identified.

Full report here;

https://www.gcaa.gov.ae/en/ePublication/admin/iradmin/Lists/Incidents%20Investigation%20Reports/Attachments/120/2018-2018%20-%20Summary%20Report,%20AIFN-0011-2018,%20HZ-AS55,%20Incident.pdf