This living wage thing is really out of hand, another form of welfare in my opinion. You contract a service for a price and that is all that should be expected. If the shop pays a guide 100$ and the guide cant live on it, he shouldnt take the job. This living wage thing is no better than going to a resteraunt and getting a 10 dollar meal and being charged 20 for it once they add on all the taxes and forced tips for you. Tips are not part of the wage. It is a gratuity for going above and beyond not for showing up. In this regard, dive masters get a raw deal. Nothing irks me more than getting on a boat after paying for the trip with DMs provided and when underway the captain gets on the speaker and says "by the way the DMs are not paid , all they get is your tips. Be nice to them because they are rigging your gear. So its guilt tipping. I hate getting a room quoted for 60 a night and paying 90. If you are going to force/guilt the tip/fee system then tell consumers up front what is expected for tips. OOPS but then this wont be a tip, it would be taxable wages ect. It is pay that bypasses the establishment book keeping. After all I dont know a single waitress that makes 2 dollars an hour. Its 2 an hour plus 200 a night of unreported tip income. Perhaps they should be tipping the customer because theey make a whole lot more than me. Lastly if a guide is going to be tipped the accepted tip should be a group tip to avoid the guilt pressuring aspect. I dont have any problem with boats that say that the DM pay will be split amongst the passengers as long as it is up front notification. After that its like using the pay toilet and then having to pay extra for TP.
100$ / day isn't a living wage. A recent article I read recently put that at around 21$/hr based on 8 hours. A living wage could be described as the income required to meet basic needs.
Granted this guide more than likely did this as a sideline or favour to the shop, I would say that at least an extra 20$-25$ a day wouldn't be misplaced. Given that you rate him as one of the 'most professional', and were very satisfied, I'd even consider a touch higher than that.