I am going to suggest you phone Canon Service on this one.
I don't see such a mode setting for the Elph 310 HS.
Canon has never released any information about how they derive those mode settings, and I doubt that they will.
Plus, the Elph 310 HS does not have manual setting ability.
Perhaps Canon Service can suggest an alternate mode to use.
Previous Canons I've owned had an underwater mode with a fish icon. I'm looking for this on my 310 HS since I just bought an underwater housing in prep for a trip where I'll be doing some scuba, but it seems to be missing from this model (firmware?)
Anyone know how I bring this up? Or if it's no longer an option, can anyone suggest what the equivalent settings might be?