I just returned from a dive trip with Blue o Two that discounted the week by 200 GBP for to get more people on the boat (yes, they are a business) but we performed 3 Reef Clean up dives and gathered about 300-400 kilos of trash from the reefs. Right now, they are the only Red Sea liveaboard that is doing this and probably one of the few in the world doing it. As a part of the trip, the dive masters conducted 4 different sessions about coral and it's importance.
I think that all liveaboards could do this on a regular basis - if not providing specific trips for it at minimum providing collection bags and guidance on how to collect the trash.
HEPCA is a non-profit that is promoting conservation in the Red Sea. They are providing education to locals, training boat captains, installing mooring lines, etc. But more needs to be done. The permenant mooring lines for the Thistlegorm were not maintained and only one is left after 15 months of being installed. All of the day boats and liveboards other than Blue o Two are tying directly to the Thistlegorm and damaging it. Also, HEPCA & the Egyptian Govt. need to begin to close some of the dive sites to divers so they can rebuild. There are plenty of dive sites in the Red Sea but they are being over used by snorkelers and divers. Again, using the Thistlegorm as an example, it is not uncommon during high season - May - October to have 200+ divers on the site each day