We are developing an underwater glider for virtual mooring. It can remain in a designated area for several years, moving between the sea surface and the seafloor up to 2,100 m deep, monitoring the sea environment. It can sleep on the seafloor or while drifting in water to extend the monitoring duration. If drifting far away from a designated area, it can glide back to the target point. If it is just at the target point, then one method to maintain its position is to glide spirally. As described herein, we present the spiral gliding tests results. We also evaluate some elements that affect the turning characteristics by simulation and demonstrate that simulation results agree well with experimentally obtained results. Results confirmed that spiral gliding is useful to maintain a position. Moreover, a small misalignment of wings can affect the rotation characteristics.