There are a few places you can dive in December. Granted it's not even close to tropical or SoCal but it's water.
Homestead: 90-95 degF, 60 ft deep, 60 ft in diameter.
Vis can be 5ft or 50 feet depending on the day.
Things to see; T-rex, one jawed gator, wagon wheel, lava type formations, lot's of silt if you even look at the bottom.
Changing area, snacks, resort lodging
SeaBase: 68-70 degF, 20-60 ft deep in three different ponds. White rocks (20ish), The Habitat(15ish), The Abyss 60'
Vis: 3-10 ft depending on day.
Salt water, tropical fish
Changing area, showers, snacks, some lodging
Blue Lake: 68-72 degF, 55 ft deep
Vis: 3-30 ft
Features: blue gill, bass, talapia, two 'wrecks', bomb, ornamental sculptures of a bi-plane, praying mantis, scorpion
No facilities...you're in the middle of nothing. Wendover Nevada is the nearest town
Belmont Springs 88-92 degF 20 ft if your lucky
Vis 5-15 ft
Features: Ahhhhh there are none unless you like minnows. Ohh wait, you'll find golf balls since it's on a course.
Changing area, showers and snacks
There are several ops in Salt Lake or you can rent equipment at Homestead or SeaBase.
Depending on where you're staying in SLC, working south to north.
Dive Addicts, Draper
Scuba Utah, Sandy
Sport Chalet, West Jordan
Dive Utah, Hollady
Neptune Divers, So. Salt Lake
If you're staying in the Provo/Orem area...god knows why.... you have Water World and Funtastic or Scuba Teds in Springville
There is also a Funtastic Scuba in Tooele which is close to SeaBase
