Water for breastfed 15 month old?

My 15 month old is still breastfeeding but he looooves water. Lately he’s been on a kick of chugging like 4-5 ounces in one stint but probably getting no more than 9-10 ounces in a day total if that. I have no idea how much breast milk he gets cause he exclusively nurses and I haven’t pumped in a loooooong long time. Is this normal? Is his water intake alongside breast milk intake too much? Or is there even such a thing? He doesn’t get milk at all. Just booby milk. Help a paranoid crazy mama out??