Abstract: An ocean-bottom node includes a node housing having an interior main cavity defined by a wall and opposite first and second ends; and one or more insert elements configured to be removably inserted into the main cavity. The insert elements and the main cavity have complementary shapes and dimensions, wherein the one or more insert elements provide internal structural support to the node housing when arranged in the main cavity. The insert elements include a structural element that prevents the node wall from deflecting inward when the node housing is subjected to compressive forces and can include an interior space configured to house any of batteries, electronics, data storage, and/or ballast, sensor, or other component. The ocean-bottom node can be a seismic node, holding one or more geophones and ancillary components.