I posted in some other thread about staying in Charleston recently. Was there 2 weeks ago for my niece's wedding. Stayed on Folly Island, right on the beach (about 15 minutes from downtown Charleston), less than 20 yards from the surf at high tide (lots of beach erosion in that area); water temps were near 80F, which was great and they're in the mid-70s as late as early October in that area (see the link). Rentals aren't cheap, but still way less than NJ: we got a 5-bedroom place with a huge great room and awesome decks for "only" $1000/night (for 4 nights; we had 5 people paying, so it wasn't too bad - and prices would be about 40% less in October).
Charleston is a great small/medium city with tons of history, including a beautiful collection of 18th and 19th century mansions, churches, military buildings, etc.- we took a horse carriage tour that was only about 90 minutes and worth it. Charleston is also loaded with great restaurants (Bourdain just did a whole show on that) and we sampled a few with 167 Raw (incredibly fresh seafood, shucked and plated right in front of you) and Grocery (lots of Low Country specialties) being the highlights. Some nice, downscale restaurants in Folly Beach, too.
As an aside, was originally going to drive the 770 miles, figuring that would be a 10-11 hour drive if traffic wasn't bad, but for a short vacation we compromised, as the wife just didn't want to be in the car that much: we flew to Charlotte, then drove the 3 hours to Charleston (about a 6 hour trip including airport time); flights to Charlotte were $200 RT vs. $600-$700 RT to Charleston. No idea if that's typical or not. Spirit flies from Philly to Myrtle Beach, but the timing of the flights was no good.
https://www.sercc.com/climateinfo/historical/coastal_water_temps.html
