crawl has 9 distinct synonyms spread across 4 of its 8 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
feel as if crawling with insects
“My skin crawled--I was terrified”
be full of
“The old cheese was crawling with maggots”
swim by doing the crawl
“European children learn the breast stroke; they often don't know how to crawl”
a very slow movement
“the traffic advanced at a crawl”
a swimming stroke; arms are moved alternately overhead accompanied by a flutter kick
a slow mode of locomotion on hands and knees or dragging the body
“a crawl was all that the injured man could manage”
Synonyms, antonyms and the broader and narrower relations for crawl come from Princeton University’s WordNet. Full sources and licences.