R.
My 18 month old is the same way (her older siblings swim and she wants to also). We tried the swim suit with built in floats and it did not work.I found her a little innertube attached to sleeves at target in the swim department. She is able to "swim" by herself (with us near by of coarse). My older 2 learned to swim independently at age 3 (they are now 4 and 6) using a speedo brand swim vest with removable foam pieces that we took out little by little.