u/Akselhe

Consider this drawing of a closed tank filled with water, say 10 meters tall. There is a thin steel straw connected on top of it say 40 meters tall, and the stick with the circular handle is a gate separating the water in the straw from the tank. To begin with the pressure in the tank is as it would be at 10m, but according to this Δp=ρgh, and chatGPT, when opening the gate the pressure would almost immeadiatly increase to 50m pressure, which would probably kill the fish, or at least kill a human diver in the tank. Is this actually how it works or am I missing something?