Something to add.
I bought the Teleconverter lens TCON-T01 and the lens adaptor, along with the Olympus floating strap on a visit to a Tioman snorkeling trip.
Some not so good experiences :
1. It's difficult to see the screen when underwater in a bright sunny day.
2. The floating strap works when there's no lens attached. It sinks when I have the TCON-T01 attached. This is quite a surprise to me.
3. The sea was rather choppy when I snorkeled, and it's quite hard to keep steady with the under current dragging you along. This results in a lot of out of focus, blurry shots.
Some good experiences :
1. The TCON-T01 can capture some pretty good close up, if you and your subject can stay still. It's nearly impossible to capture good pics of fishes that darts around. Sea anemones, burrowing clams, sea urchins and corals are the easiest to shoot.
2. Picture quality is pretty good, as expected of an Olympus camera (as shown by a forum poster above).