Although permanent ocean-bottom cables installed at the Valhall field record high-quality and repeatable active seismic surveys, even in absence of active seismic shooting the array can record an abundance of seismic energy. Seismic interferometry of 29 hours of passive seismic data generates omnidirectional Scholte-wave virtual-sources at very low frequencies (0.4−1.75 Hz). Scholte-wave group arrival times are inverted using both eikonal tomography and straight-ray tomography to reveal features that match with known geology in the upper 100 m beneath the ocean floor. This technique can form a very low-cost near-surface monitoring system using seismic noise recorded by permanent ocean-bottom arrays.