CZ Tarantule was supposed to be used in cases where explosives couldn’t be used due to a high risk of collateral damage. The Tarantule uses a modified .50 caliber blank round loaded from the breech of the 18mm caliber smoothbore barrel to propel the 70ml of water which is poured down the muzzle and sealed in the bore via a special plug. The muzzle velocity of the water jet is a whopping 3500 m/s or 11,483 fps.

https://www.thefirearmblog.com/blog/2022/04/27/cz-tarantule-prototype-water-cannon/