I've noticed while emptying water temples of water using sponges, that guardians will continue to spawn inside, irregardless of the rooms no longer having water in them.
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Point 1. "Irregardless" means "not regardless" and is not a word, as well as the exact opposite of what you said.
Point 2. It doesn't matter if they can live out of water, they shouldn't spawn out of water.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.
gaurdians are able to live without water, they don't breath at all 😃