The question "Why does the white limestone have to come by water?" is a bit tricky. It's important to understand that limestone itself doesn't have to be transported by water. However, the formation process of most limestone heavily relies on water. Let me explain:

* Formation of Limestone: Limestone is primarily formed from the accumulation of the skeletal remains of marine organisms, such as corals, shellfish, and plankton. These organisms extract calcium carbonate from seawater to build their shells and skeletons.

* Water's Role:

* Dissolving Calcium Carbonate: Water plays a crucial role in dissolving calcium carbonate from rocks and transporting it to the ocean, where marine organisms utilize it.

* Sedimentation: When these organisms die, their shells and skeletons settle to the seafloor, forming a layer of sediment. Over time, these layers get compacted and cemented together by further dissolved calcium carbonate, forming limestone.

* Erosion and Transportation: While water doesn't always directly transport limestone itself, it can erode existing limestone formations and transport the resulting sediments to new locations.

Therefore, while limestone itself doesn't have to be transported by water, water plays a fundamental role in its formation and can also transport limestone sediments.

Important Note: There are some instances where limestone can form in non-marine environments, like caves and hot springs, but these are less common than the marine formation process.