Here's why:

* Clastic means the rock is made up of fragments (clasts) of other rocks or minerals.

* Coquina is specifically formed from the cemented shells of marine organisms like clams, snails, and other bivalves. These shell fragments are the clasts.

So, even though coquina is made of organic material, it's still considered a clastic sedimentary rock because it's composed of cemented fragments.