Makes sense in Japanese, where "holy water" and "piss" are homophones.
It's /shousui/ instead of /seisui/ though. "Holy Water" is only used to refer to urine in a urolagnia context (directly or obliquely), like English "golden shower".
As for Asashio, she gets harassed by her Commander all the time for her urine, so even the most innocent of minds would have picked up what 'holy water' means in the slang sense.
Shaved ice's definitely a must for summer, right!Yes, it is delicious and makes you feel cool.By the way... doesn't the condensed milk sorta look like sem*n?NEXT DAYICEICECommander! What does 'sem*n' mean? Could you teach it to me, please?I'm curious.Fwah!?Two birds in one stone, so to speak.