Video housing dome ports are best for use with wide angle lenses. and standard camcorder lenses. They mostly allow close up to very wide angle usage, but not full zoom-through.
The new Olympus OM-D E-M1 MKII has been the darling new camera lately, with high reviews from all corners for its improved feature set. The combination of a wide range of superb PRO lenses, fast speed, and incredibly rugged build quality has everyone thinking about this m4/3rds camera as the answer for a smaller, high performance underwater platform.