>>6727815From a character standpoint, it serves to explain her robotic personality and her distance from the other characters; her inability to feel close to the people who are close to her. In the final act, Batou expressed geninue concern for her, but she couldn't care less about his feelings or motivations. It's not to say that she's not grateful for him, but she'll never feel close to what he feels for her, regardless of whether or not you think he loves her.
Water is also a very spiritual symbol, evoking a sense of birth, rebirth, or cleansing power. This may provide some insight into how Motoko feels about herself; her self-judgements and self-worth.
Lastly, from the cyberpunk angle, it can be seen as evolution coming full-circle, simultaneously coalescing into a new paradigm of human existence (providing, perhaps, the strongest connection to real-world themes and thoughts). At this point, the marriage of humans and technology--if not technology itself (through parasitism or symbiosis)--has attained lifeform status, and as all creatures on Earth have done, it has risen from the primordial ooze, free to roam on land and live at the whims of natural selection. This theme is reinforced in the final act's tank battle, when the tank's machine gun destroys the Tree of Life relief, with homo sapiens at the top of the tree--perhaps a successor has been chosen, or a usurper has appeared, or maybe the old conventions simply do not apply anymore.
Maybe a little too in-depth for /wg/, but GITS has been booty-calling my brain since the early 2000s, when I first watched it as a kid.
