Desalination Plant (Unimplemented)
The Desalination Plant was a utility building designed to provide water for your Sims where Salt Water was available.
Desalination Plants were designed to be placed next to oceans and provide water when the amount of Fresh Water was insufficient.
Development on the Desalination Plant was probably halted at the same time that work on the Weather and Water Table simulations were also halted. There are only remnants of this plant in the game's code and the community has created lots which implement this functionality. However, like implementations of the Water Pump and Water Tower working on the Fresh Water part of the simulation, they do not function predictably due to the code being incomplete.
An icon for this building is possibly in the game's files which indicates it may at least have been in the game's Alpha version.