Difficult to answer because I don't know how advanced your tomato plants are in their growth. Their root systems are probably too well established now for you to dig them up and plant them somewhere else, especially in this heat which would make them wilt badly. Unless the flood water contained sewage or some other toxic effluent, you may just have to accept that you won't get a good crop this year and hope for better luck next time. With time, they may pick up if the soil dries out a little. If you can still get any good quality late small plants from a garden centre you could try growing a few newplants in grow bags.