Oly has a prime fisheye and the 7-14. I would think their wide options are fine given no personal experience with them. It's the macro that bothers me. A 100mm would be very long on the 4/3 sensor but the Sigma exists for it though I've never seen anyone house the Sigma 105. The midrange zoom could substitute for the short macro. I believe the 50, the 7-14 and the 8mm FE could make a good set if you added the 1.4x for macro and possibly the 14-42 for portraits. It's just that Canon/Nikon offer more options.
With respect to lenses, Oly does offer a 7-14 rectilinear wide angle (14-28 in FF equiv, vs. ~15 - 25 equiv for the Tokina). Clearly not 'equivalent' as rectilinear vs. FE although covering very similar focal ranges, for similar uses. And it does have an 8mm fixed FE. Neither is cheap, the former much more expensive than the Tokina no less, so I'm not trying to claim both equivalent coverage and less expense. Just offering the info for the OP's consideration. The missing 100mm macro (aside from Sigma) is clearly a remaining sore void in the Oly world.
I've never made any comparisons regarding Nikon vs. Oly prices but, Ardy, you continue to insist that Oly is cheapest while assuming that nothing less than Oly can meet your arbitrary and vague quality standards. If you don't need "the best" then who's to say that a digicam at far less size and cost wouldn't be good enough?
It was much cheaper for me to sell my Nikon gear and totally move to Olympus than to just buy a camera and housing + ports.
You are entitled to your opinion on lens selection, but Nikon and Canon win on more than just high ISO. Nikon and Canon offer better IQ at base ISO as well.
Oly wins on price, size and weight with its selection of underwater DSLRs. The only place oly loses with Canon and Nikon is in ISO's past 800 which isn't useful underwater in most cases. Lenses? There are plenty of selections for an olympus user.
As I said, you are entitled to your opinion on lens choices but if you think adding a Sigma 105mm (a lens too long for most on 4/3) and a 35mm f/3.5 (that's still a bit long and is slow focusing) is going to sway people into thinking 4/3 is a competitive macro solution I don't agree. The Oly 50mm and 35mm both have received complaints for their slow focusing and the Sigma 105mm extends massively making it difficult to house (and it is a slow focuser as well). I believe a 4/3 user would want manual focus with the 105mm and that lens does not switch between MF and AF easily. Regarding wide angle, rectilinear shooters may be quite happy with the Oly choices but DX shooters have comparable options plus a far superior fisheye choice. It all boils down to what you mean by a "complete line".
Given the above complement of lenses, I think its being misinformed to say Oly doesn't offer a complete line of underwater lenses.
The expense, size, and weight of the entire system needs to be considered as one component is rather meaningless unless it is optional. Once you add the size, weight, and cost of everything together the differences aren't nearly what's being represented here. If Oly pro glass is required to get the lens options necessary for underwater, then it's not really optional is it?
Expense of the pro glass. - There's some excellent topside glass but it comes at a huge price. Even the Sigma options are expensive.
When have I said otherwise? This kind of cheap-shot arguing is unwelcome. The whole suggestion that the Oly is radically lighter than all other DSLRs has already been debunked. Sorry you had such a hard time managing your Aquatica F4 but it isn't relevant. Not all Canon and Nikon DSLRs are as massive as an Aquatica F4.
contrary to what Craig thinks it hurts like buggery when the 50th wave jars 10+kgs it into your thighs