Abstract: An annular vehicle having a body which defines a body axis and appears substantially annular when viewed along the body axis. The interior of the annulus defines a duct which is open at both ends. The vehicle includes an electric field (EF) coupled dipole antenna arrangement for electro-magnetic communications, which includes at least one dipole antenna. The vehicle is used as a node in an underwater communications system for communicating with other node(s) using their EF coupled dipole antenna arrangements. The electric field coupled dipole antenna arrangement can provide communications with lower latency than systems employing acoustic communications. The annular body provides good separation for electrodes of the EF coupled dipole antenna arrangement disposed around the body.