<p>Underwater superoleophobic materials have excellent underwater oil resistance due to their special wettability surface, which can cope with oil spill accidents and oily wastewater treatment. In recent years, metal-based underwater superoleophobic materials have attracted tremendous attention in the field of oil–water separation. However, the current methods for fabricating underwater superoleophobic materials have some shortcomings, such as complex preparation process, high cost, and secondary pollution. In this work, calcium carbonate nanoclusters (CaCO₃–NCs), the product of thermal decomposition of calcium acetylacetone, were anchored on the surface of stainless steel mesh (SSM) by impregnation-combustion method to fabricate an underwater superoleophobic material (CaCO₃–NCs@SSM). The samples were characterized by field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), energy-dispersive X-ray spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and X-ray diffractometer (XRD). These results show that CaCO₃–NCs can be uniformly and compactly anchored on the surface of SSM by impregnation-combustion method. Moreover, the oil–water separation capacity and the reusability of the samples were also evaluated by a self-made oil–water separation device. CaCO₃–NCs@SSM possesses excellent underwater superoleophobic property because of its uniform and dense hydrophilic micro–nanostructure on the surface, which can absorb water to form a water film. It can also be known from the contact angle test that the underwater oil contact angles of ethyl acetate, corn oil, dichloromethane, chloroform, liquid paraffin, and diesel oil on the material surface are all greater than 150°. Furthermore, the sandpaper abrasion test demonstrated that CaCO₃–NCs@SSM has excellent mechanical durability. In the oil–water separation experiment, the separation efficiencies of this material for different oil substances all exceeded 98%, among which the separation efficiency of chloroform was 99.5%. In addition, CaCO₃–NCs@SSM maintains a separation efficiency of more than 97% over 60 consecutive cycles of oil–water separation. In summary, the underwater superoleophobic material proposed in this paper has a facile preparation method and high oil–water separation efficiency, which has great potential in solving oil spill accidents and oily wastewater treatment problems in harsh environments.</p>