Don't know any names, but look for beaches that have a
part "sealed off" by a half-circle of logs or similar.
They break the waves, almost eliminates the undertow and often
come with a shark-net underneath. Depends on how "novice" swimmer
you are. If very novice, I'd probably recommend a few days
practice in a pool before hitting "the real thing"! Notice
however that there are many places where you can "play" in the
water without any swimming capability whatsoever! There are
many dominicans who don't swim at all! Look for the places where
the children play, these are very calm. Even if I swim quite
good, I often go there, just to float, enjoy the sun, and maybe
have a "floating nap" after lunch... (The latter is not
really recommendable unless the part is sealed off. You may wake
up a little bit farther from the shore than you'd really wish.
Happened to me a few times in Miami, and it can be quite
exhausting to get back against an outward drift...)
Welcome here, and I hope you will have a wonderful stay!