Without them the polyps of the tropical hard corals would be unable to build the huge coral reefs of tropical waters.
(the polyps of the tropical hard corals; would be; unable to build the huge coral reefs of tropical waters) (the polyps of the tropical hard corals; to build; the huge coral reefs of tropical waters)
the polyps of the tropical hard corals the polyps of the tropical hard corals
would be to build
unable to build the huge coral reefs of tropical waters
the huge coral reefs of tropical waters