I am a divemaster for a shop north of Denver and president of a dive club here. As for local diving, we dive Aurora Reservoir (31 feet deep and a Cessna 310 wreck to dive on), Chatfield Reservoir and a bit north of the city is Horsetooth reservoir (Ft. Collins) and Carter Lake (Berthoud). It tends to be colder water, even in the summer (72 at the surface, 60 below the thermocline). The visibility locally tends to range from 2 to 15 foot, with the best vis in the winter as we have algae and silt. 7 mm or drysuit is advised locally.