What are the available scuba trip options and when should I use them?

When creating a dive trip, the following days of diving options will be made available for use:  1 day through 30 days, and unlimited AND the following number of tanks options will be made available for use: 1 through 30, and unlimited AND the following breathing gas options will be made available for use: air, nitrox, trimix, helitrox, heliox, hydreliox, hydrox, neox, and other; a single option for days of diving, number of tanks and breathing gas must be specified for each dive variation and that combination of options must not be used more than once.  These options are useful to help distinguish the pricing for the dive trip.