“My understanding is that if you drink water for pleasure, you say shehakol. But if you drink water simply to keep yourself hydrated, you don’t say a blessing.”
You have seriously misunderstood the halacha. Drinking to keep yourself hydrated is the only case when you DO say the bracha, since that is the only case in which you derive benefit. It is OTHER uses, such as washing down pills or bile, that do not have a bracha, because one gets no benefit from ingesting the water.