The Underwater lenses tag complements underwater imaging by focusing specifically on lens designs intended to function in or behind water-filled environments. Articles here may discuss how focal length, field of view, and distortion are affected by immersion and how designers compensate using specific geometries and glass choices. Topics include the use of domes versus flat ports, sealing strategies, and coatings that resist biofouling or scratching. The tag highlights lenses used in diver-held cameras, remotely operated vehicles, and fixed underwater observatories. For system developers, these resources explain how dedicated underwater lens design differs from repurposing air-optimized lenses and why custom optics often yield better performance and reliability. They demonstrate Avantier’s expertise in creating lenses that deliver sharp, stable images under water while withstanding the mechanical and environmental stresses of subsea deployment.