best below-butt moves?

even if i am below my target weight, working as long and hard as i can, i still can seem to tighten and smooth that godforsaken spot visible in my bathing suits and some shorts.

what is the best solution?????

I don't think I need to focus on my glutes. . i've kinda got the J Lo thing going. And I work out in the gym, if that matters.
I like to keep it fairly simple. If possible, but if it works . . I'LL DO IT!

appreciate it.