Why does the Araquanid I caught in Sw/Sh have Water Absorb and not Water Bubble?

Question

I found an Araquanid in a Max Raid Battle and thought I should get it since Water Bubble is op. I successfully defeated and caught it, but it had Water Absorb despite it being its Hidden Ability.

Comments

use a ability capsule if you dont want it

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Ability Patch is the one that changes HAs, not Ability Capsule. Though, it will only change a standard ability to a HA, not the other way around.
You can just breed/catch another one in any case.

Answer 1

The caught Pokémon's moves and Ability will be the same as it was during the Max Raid Battle; some Dynamax Pokémon encountered in Max Raid Battles will have their Hidden Ability.

It's possible to catch Pokemon with Hidden Abilities in Max Raid Dens.

Max Raid Battle (Bulbapedia)