Electrochemical reactions are typically suppressed by surface-adherent gas bubbles: the gas cavity blocks ion movement and electrode–electrolyte charge transfer processes. Here, we report the unexpected finding that bubbles can enable confined electrochemistry in nanometre-thin aqueous films trapped between bubbles and solid electrodes. These films, measuring 1–6 nm in thickness, are sustained spontaneously by repulsive van der Waals interactions. Despite their minimal volume, these interfacial water layers support ion migration, double-layer charging, and mass transport via Marangoni flow. This novel hydrophobic/van der Waals (vdW) nanoconfinement environment challenges the common perception of bubbles as detrimental, blocking entities, and offers a straightforward strategy to (i) enhance electrochemical reversibility and (ii) localise redox enzymes near a sensing electrode. A key application is illustrated by trapping oxidoreductases in the first electrochemical glucose biosensor that operates on a bubble.