T1 questions

Some of the sprints I've done coming off of a beach have had you run through a series of wading pools to wash the sand off your feet. But not all, so check with the race director if this is a concern of yours. IMHO tubs of water in transition should be outlawed as more often than not they get spilled or in someone's way. A water bottle and a small towel should be sufficient.

I run without socks in sprints without a problem, but I'd try it in training first.

You won't have a hose to run through at a sprint.  Some people use a small (small) basin.  I just use a water bottle at T1 and quickly spray the sand off my feet.

Re: socks - depends on you.  I can do 3 miles without socks.  Over that I get blisters.  Others can got half marathons sockless.  Whatever you do, make sure you practice it before race day!