The Lewis base character of the greenest reagent water has been explored with regard to its nucleophilic property for an organic transformation. Utilizing this concept, a new strategy for the highly controlled and selective mono-dehalogenation of α,α-dihalo ketones has been discovered and is reported in this contribution. Extending this concept, the first direct conversion of propargylic acetates to the corresponding α-iodo ketones via α,α-dihalo ketones has also been efficiently achieved under metal-free conditions. During the latter process, water has been concurrently employed as a nucleophile and a Lewis base. This may be the first report of the employment of this type of dual reactivity of water in the context of organic synthesis. Control experiments support the involvement of the enolate as an intermediate during the monodehalogneation process.