Aquariums: Was I meant to see this? (A fun snail centipede or a freaky orgy?)

Yeah so, what in the ever living fuck did I just happen to walk past?

I have two other snails in the tank that happened to be cruising by reeeaaaaalllll close.

Is this normal? Is this a broken matrix moment?
How does this happen?

This seems unholy as fuck, and I’m just wondering if I’m meant to be feeling this disturbed.