The lifeblood of global communication flows through more than 807,800 miles worth of garden hose-wide cables woven across the sea floor. The Associated Press estimates that at least 11 cables have been damaged since October 2023 in the Baltic Sea alone. Fears of escalating subsea cable sabotage have even prompted NATO to ramp up its military surveillance presence in the region through an all-hands-on-deck mission dubbed “Baltic Sentry.”But keeping tabs on the Earth’s subsea cables is easier said than done. Optics11, a maritime‑defense company based in the Netherlands, is trying to solve that growing problem with OptiBarrier, an underwater surveillance system it claims can “listen” using light. The company says OptiBarrier amounts to a “network of sensors” on the seafloor, capable of detecting minute variations in the way light travels through the cables.