Described herein is a seismic node, comprising: at least one seismic sensor; a pressure resistant structure having a first wall, a second wall, and one or more supporting elements extending between the first and second walls to define one or more cavities for containing pressure sensitive components; and a separate waterproof sealing skin surrounding the pressure resistant structure and the at least one seismic sensor. Also described herein is a method for producing a seismic node.

A hydrophone has a mandrel with a shell and a cylindrical cavity inwardly adjacent to the shell. A passage provides fluid communication between the cylindrical cavity and an exterior environment surrounding the mandrel. The hydrophone further has an optical fiber having an optical sensing section that is at least partially wound on the mandrel. The optical sensing section has an optical characteristic that varies as a function of a radial dimension of the mandrel. The mandrel has a core of solid material having a bulk modulus lower than 0.1 GPa. The cylindrical cavity is between the core and the shell.