Aiming at the issues of long communication delays and offline processing caused by data preparation and training in machine learning-based vortex beam orbital angular momentum-shift keying(OAM-SK) communication schemes, this paper proposes an OAM-SK communication scheme for underwater vortex beams based on spiral spectrum detection. This scheme enables the recognition of the mode of the vortex beam by directly performing spiral spectrum calculations on the optical field of the received vortex beam at the receiver end, thereby achieving information transmission. The simulation results show that although the proposed scheme has slightly lower reliability, it significantly enhances the effectiveness of the communication system.