The Slocum Glider is a commercially available autonomous underwater vehicle used in the sensing of the world's oceans. Its manufacturer-provided simulator uses nearly identical electronics and components as installed in the production glider. The simulator is mainly used to develop and test new hardware and software components in a real-time setting, where for instance, a one-week mission of the glider takes one week to simulate. This limits the types and the complexities of algorithms that can be developed and tested on the vehicle. In this paper, we present our ongoing work on a simulation infrastructure used to fly and operate a Slocum Glider in a virtual ocean environment. We also introduce a new three dimensional companion visualization tool. The effectiveness of the infrastructure and its new visualization tool is illustrated in the context of three applications, namely glider education and training, the replay and analysis of glider missions, and the design and testing of algorithms to be used in future missions.