Water is always used by nature to construct complex species. Learning from nature, the exploration of artificial approaches to utilize abundant water to synthesize functional molecules and polymers with efficient clusteroluminescence properties (CLgens) is highly significant but has yet to be reported. Herein, a new chemistry of water and alkyne was developed. The synthesized products were proved as nonaromatic CLgens that could emit visible light. Their emission colors and luminescent efficiency could be adjusted by manipulating through-space interaction via using different water and alkyne. Besides, the free-standing polymeric films with much high photoluminescence quantum yields (up to 45.7%) were in situ generated via a new H2O-involved interfacial polymerization. The interfacial polymerization-induced emission of the polymeric films was observed, where the emission red-shifted and efficiency increased when the polymerization time was prolonged. The synthesized polymeric film was also verified as a "Janus film". It exhibits a vapor-triggered reversible mechanical response which could be applied as a smart actuator. Thus, this work develops a new method to synthesize CLgens using water, builds a clear structure-property relationship of CLgens, and provides a novel strategy to in situ construct functional H2O-based polymeric films.