What is the origin of the lake tank image that has become a meme? (2021)

Since Know Your Meme doesn't give the reference for why it's a lake, maybe not everybody is familiar with british lore:

The mythical Lady of the Lake:

Probably best known via Monthy Python:

Strange women lying in ponds distributing swords is no basis for a system of government. Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony.

In short: She teaches Lancelot arts and writing, infusing him with wisdom and courage, and overseeing his training to become an unsurpassed warrior.

https://en.wikipedia.org/wiki/Lady_of_the_Lake

https://tvtropes.org/pmwiki/pmwiki.php/Main/EnigmaticEmpower...