As is seeming to become a theme, I echo RJack's sentiment on mix. I do think a 12L at 260bar is ~110cuft of gas though.12L = 85cf steel in imperial terms.
If you want to be doing 50m dives and taking (good) pictures at Bikini you need trimix. Helium is not practical there for open circuit. Thus you need a CCR. If a CCR is too big a commitment to develop the skills and mindset to use, I'm not sure being on air at those depths for a casual "vacation diver" is any wiser.