Organisms take advantage of this chemistry and locally manipulate it to precipitate their skeletons. It's the same in the oceans. At higher T, it is easier to precipitate carbonate so you get coral reefs in warm, tropical latitudes, for example, Florida, the Caribbean, equatorial Pacific islands, etc. Extensive carbonate deposits are less common in colder water. There are carbonate secreting organisms, as you know from seeing shells on the beach, but they are a substantially less abundant in sediments because it is very costly for the organisms to make them because it is much harder to precipitated carbonates in cold sea water.
Agitation produces pockets of low pressure where gas bubbles can form.
This is one of the reasons reefs develop so nicely - the crashing waves make it easier for the corals to precipitate carbonate by locally removing CO2. In contrast, the deep oceans have much higher pressure due to the overlying water column. Organic matter decays to CO2 as it settles from the surface waters. That CO2 remains dissolved in the deep water making carbonate dissolve in deep water. Given the geochemical background, we will return to the biological processes.