Methods and devices for accessing a body cavity are disclosed. In general, a trocar assembly is provided that can include a housing having a cannula that extends therefrom to define a working channel that is sized and configured to receive a surgical instrument. The trocar assembly can also include a seal unit that is disposed in the housing. The seal unit can be generally configured to allow off-axis insertion of an instrument through the working channel without lateral movement of the seal unit. For example, in one exemplary embodiment, the seal unit can be rotatably disposed in the housing and have at least one seal element that is adapted to selectively seal the working channel. The seal unit can also be adapted to rotate about a longitudinal axis of the assembly and an axis perpendicular thereto.