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...

Note that, at least in Thomas Malory’s telling, the arm holding Excalibur out of the lake is not the Lady Of The Lake, who is nearby on the lake. The arm holding Excalibur is neither named nor explained.