Have done a lot of diving in Eilat, including my DM and AI this summer and a week between xmas and NYE last year.
The water temp is around 21 in Dec but as someone mentioned, the wind can be a killer on the SI. I dove with a full-length sharkskin and a shorty over the top and was v comfortable in the water. outside was a different matter. Did a night dive in Dec and wore a 5mm full suit
No liveaboards in Eilat - it's not necessary. a few of the dive shops have boats to get to a few of the site sonly accessible by boat (Japanese Gardens for instance)
Lots to see - I think Nudibranch season kicks off in January, so if you're interested in those, it can be spectacular. On my various trips, i have seen: whale shark (usually visits in the summer), stingrays, eagle ray, turtles, dolphin (let out from the Dolphin reef), lots of nudis and eels, lionfish, stonefish, scorpion fish, ghost pipefish, various types of shrimp, barracuda, frogfish etc etc.
Worth visiting the Satil a couple of times. a very easy wreck, at 25m max. The Yahalat is at 50 and the Yatush at 30 (not very interesting). the underwtaer restaurant at the very north of the bay is very cool - rubbish vis but lots and lots to see
I always dive with Shulamits Eilat Diving Adventures (
Shulamit's Eilat Diving Adventures - PADI diving courses and guided dives in Eilat) - i think it costs a little more but it has much less of a "factory" feel than the bigger dive shops mentioned above (i've also dived with Aquasport, U-dive and Manta). She tries to limit group size to 4 and provides free nitrox if qualified. The instructors are fab and they also have a boat to get to the Japanese Gdns. She also provides boots, which are essential for shore entries, and does free hotel pick-up and drop offs (don't judge by the state of the cars though
) Hire gear all top notch
You can also pop across the border and dive in Jordan for a day, they have a big wreck (the Ceder Pride) and a tank. the topogrphy also means they have a big drop-off (Lighthouse), which is spectacular, if that's your thing. Occasionally see reef sharks there. I dove with Ricky at Ahlan
Egypt also accessible for day trips - Aquasport has a sister operation in Taba, with a boat to take you further south. it's pretty good but the border control is a PITA.
Hope helpful
enjoy your trip - pm me if you want more info