Have you considered swimming lessons? Children as young as 15 months can swim
Swimming lessons start from 3 months. Around aged 2.5 is when they go to lessons independent from their parents.

Im a swim instructor and we are taught that floaties interfere with children learning how to float independently and keep their bodies up when swimming.

However..............I have 3 children all under 5 and when my husband and I take them swimming we only have so many arms to hold them. For safety because they love swimming and have no fear they wear swim vests. I always make sure I take them off them one at a time and get them to practice their swimming for about 15min but otherwise they wear them; at the beach or pool.

I definitely think swimming lessons are an absolute must for all children but I would never tell a parent not to use a flotation device for safety's sake. I would only recommend a swim vest until the child can swim unaided after taking lessons, the arm floaties and back floatie would only really be useful for a child who has the swimming movements learnt but has trouble staying above water on their own.