StiX floats are the easiest way to lighten up a heavy DSLR system underwater. Made by 4th Generation Systems, they are easy to put on and can be cut away as necessary.
Buying the best lenses - and ports to use them in, can be a long-term value investment. Lenses and ports can be used over and over as you buy new cameras. Buying high-quality lens solutions as you can afford them is the best plan. However, planning what lenses to buy and what format to invest in is a very important decision.