As you enter the money pit we call underwater photography, there will be no end to the "here's what you need next" suggestions. We all have our favorite things. I am finding that the set up I like best right now for my E-PL2 is the 14-42 kit lens behind the Zen dome port. It gives you a true 24 -84 (35mm equivalent) lens that lest you shoot fairly wide angle but still zoom in and shoot macro. I add an Inon close up lens on the Oly adaptor and it gives me a lot of flexibility. If you aren't sure what all you will see on a given dive, this is the most flexibility you can get. If you know you want wide angle (barracuda and sharks at Sipadan) the 9-18 and Zen is great. If you know you want macro (muck diving at Mabul) then the stock flat port and 14-42 are the way to go. If you have the option for needing both (anywhere on Bonaire) then the 14-42 behind the Zen is ideal.
I spent 5 years shooting an Oly C5060 and got very used to being able to shoot some "wide" and "macro" on the same dive. I freely admit I have not spent enough time with the 9-18 lens underwater yet to really learn how to use it properly. I have figured out that when I have it on, I cannot shoot what I would call "macro" at all as it just doesn't work. You can do CFWA (close focus wide angle) with it but I am still not that comfortable with it to be any good. I have realized that, for me, whatever I put behind the Zen dome looks better with a two flash set up......there's my suggestion for the money pit! Good luck.
I spent 5 years shooting an Oly C5060 and got very used to being able to shoot some "wide" and "macro" on the same dive. I freely admit I have not spent enough time with the 9-18 lens underwater yet to really learn how to use it properly. I have figured out that when I have it on, I cannot shoot what I would call "macro" at all as it just doesn't work. You can do CFWA (close focus wide angle) with it but I am still not that comfortable with it to be any good. I have realized that, for me, whatever I put behind the Zen dome looks better with a two flash set up......there's my suggestion for the money pit! Good luck.