Answer:
It is the great nemesis of the lactose intolerant.
Looks like water, but it's heat. Sits on sand, lays on concrete. A play on the eyes, but it's all lies.
What word is a plural, but when you add an "S" to the end, it becomes singular?
Salty water everywhere but not sea in sight.
Two brothers we are, great burdens we bear. All day we are bitterly pressed. Yet this I will say, we are full all the day, and empty when go to rest.
What covers its face with its hands, speaks no language, yet most known what it's saying?