Lake Havasu usually has 5 feet or less of viz. The lake is pretty shallow - about 40' at the river bed. I don't think Joel dives the lake. I know that the other shop in town, that does dive the lake, wasn't very enthusiastic about it when we were there. There's only one area that's might even be worthwhile diving from shore (it's off the island), but it was so dark and murky when we dove it we couldn't even find the boat that's supposedly sunk there. We might head back that way some day, but there are better lakes to dive.
Lake Mohave is definitely the best lake in Arizona to dive. I've never seen viz less than 10' and that was during a storm. Viz is usually 20-25'. There's a bus, van, and boat right off Cabinsite, and you can get to 80' within minutes of stepping into the water. Interesting topography there. It's definitely worth the drive and during the week you can get a hotel room in Laughlin (only 10 minutes away) for about $25/night. The one drawback is there are no local shops. The closest air fill is about 45 minutes away in Kingman. So bring you own tanks. If you plan a Mohave/Vegas trip, you can top off in Vegas.
Lake Mead is okay to dive if you happen to be in Las Vegas anyway. We usually head up and dive Mohave a couple of days, drive to Vegas to hang out, dive Mead one morning to get wet and cool off, then hit Mohave on the way back home. Mead's water level has been dropping a lot over the past few years. It's down over 100' right now. They will probably have to move the marina soon (actually, they should have moved it last year!). The only shore accessible area is the scuba park and there's not much to see there. They used to have a few attractions there, but the dropping water level has caused them to have to move most of the attractions to other locations. Mead has some good boat diving sites, but it's not easy to find a dive boat that's going out. The local shops don't think much of Mead. If you head up that way, contact LakeMeadTony here on the Board. He has a boat and will go out if his schedule permits.
I haven't been to Powell, but from what I understand it's in the same predicament as Mead. The water level is down over 100'. They spent about $2 million last year moving one of the marinas.
Soon we'll all be able to hike the lakes in Arizona! :frown: