pływać kraulem Englisch:

Her son started to crawl.

to crawl to sb

crawl1 /krɔ: l; US / verb [intransitive] 1 to move slowly with your body on or close to the ground, or on your hands and knees Their baby has just started to crawl (raczkować). An insect crawled across the floor. ▶ pełzać czołgać się