Last week, it was so mild that I almost had to put my hands in my pockets. Where I live there are dozens of excellent dive sites for both day and night diving, for divers and conditions of all skill levels. There's one dive with eels, octopi, and thousands of fish, and you couldn't get lost if you tried. I've only been to one dive that's had to be called for conditions, and that was so bad that there was a huge red snapper (25+# easy) that the seagulls couldn't land on to snack on.
Summer visibility in the inlet gets up to 100' or so, and gives a striking black background. You can see all manner of critters just floating in the middle of nothing...
And if all goes to hell, the Navy has a dive chamber that you can borrow.
On the downside, the critters aren't as colourful as on PADI's website. Also, the water ranges from 4C - 7C over the course of the year, so drysuits are more-or-less mandatory, even when it's 30C on the surface. I've actually had a sunburn and mild hypothermia on the same day.