Even with intensive research, air-stable blue light emission from silicon nanocrystals (Si-ncs) at room temperature still remains a challenge. We show that stable and blue-luminescent Si-ncs can be produced by laser-generated plasma (nanosecond-pulsed excimer laser) confined in water. These Si-ncs exhibit quantum confinement effect due to their size and are produced with an environmentally compatible process. The effect of aging for several weeks in water and air on blue Si-ncs emission properties is compared. The oxide shell around the nanocrystalline core formed during laser processing in water offers the required conditions for the confinement of excitons that allow for stable (in either air or water) blue photoluminescence at room temperature.