a congregation of alligators ConfidencehighAttestationwikipedia-citedAlso used forbirds, crocodiles, people, ploversAlso spelledCongregacōn (1486) 2 sourcesWikipedia - List of animal namesZoological Society of San Diego - Animal group names
a bask of alligators Context-dependentFanciful / unverified Contextbasking in the sunConfidencelowAttestationwiktionary-wordlist-onlyAlso used forcrocodiles 2 sourcesWiktionary - baskWiktionary - Appendix:English collective nouns