Why not offer 28%???Quero:What a thrill to see the hammerheads! Was it a big school?
As for the unavailability of nitrox, well, the thing with nitrox and L2 is the depth of the dives. About half of my dives there were deeper than 33 m, which is the depth limit for 32% nitrox fills (assuming a 1.4 opp limit). It's just not practical from a safety standpoint to offer nitrox at L2.
Just becuase there are tables for 32 and 36, you were trained how to calculate for other mix's. 28% works well at 40m and boosts your bottom time somewhat