A retractable entry/exit system for a boat that mounts below a swim platform or other similar boat structure. The system has a main frame, a linkage, a number of step assemblies and a single actuator. The actuator is configured to move the linkage to selectively extend or retract the step assemblies. When retracted, the system is folded into a compact arrangement under the mounting structure. When extended, the step assemblies extend beyond the mounting structure, where they can be used to conveniently enter and exit the boat or as a place to rest, lounge, sit or otherwise enjoy the water. The linkage may include a bell crank assembly with integral linkage arms, as well as a pair of supplemental linkage arms. The linkage arms may be disposed toward opposite sides of the system and may be operatively coupled to step brackets that support opposite ends of each step assembly.