How might babies swim? (5)

I believe the answer is:

crawl

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'swim?' is the definition.
(crawling is a kind of swimming)

I can't explain the rest of the clue.

(Other definitions for crawl that I've seen before include "progress slowly" , "Go slow" , "Move slowly (as a baby does?)" , "making slow progress" , "Go on all fours" .)

I've seen this clue in the Sydney Morning Herald.

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