High‐Power Graphene Thermoacoustic Underwater Sound Source Assisted by SEBS Micromesh Matching Layer

High‐power failure restricts graphene thermoacoustic performance, necessitating a strategy that synergistically enhances acoustic output and mitigates surface heat. Laser‐induced graphene (LIG) thermoacoustic sound source (TASS) is integrated with an aqueous cooling environment, while a hydrophobic styrene–ethylene–butylene–styrene (SEBS micromesh is introduced as a multifunctional interlayer. By preventing direct contact with water, the mesh layer suppresses the attenuation of surface temperature oscillations induced by water absorption. Meanwhile, the confined gas phase retained within its porous architecture sustains pore‐scale volume oscillations and preserves the thermoacoustic energy‐transformation process. The micromesh provides acoustic‐impedance matching, promoting efficient transmission of generated acoustic energy into water and enabling underwater radiation without altering the gas‐phase actuation mechanism of the TASS. Benefiting from enhanced heat dissipation by water cooling and the isolation/matching functions of the micromesh, the SEBS micromesh‐assisted LIG TASS (SML‐TASS) exhibits markedly increased allowable AC input power and higher attainable sound pressure level (SPL). Under a unified measurement framework, the SML‐TASS delivers pronounced SPL enhancement over 2 kHz–5 kHz and reaches a maximum SPL of 109 dB. Underwater characterization further demonstrates stable ultrasonic emission across 20 kHz–140 kHz, validating its feasibility as an underwater ultrasonic radiator. This work establishes a generalizable interfacial design for solid‐gas‐liquid thermoacoustic conversion.