Objective: To investigate the genetic mechanism and prevalence of antibiotic resistance among the practitioners of two bathing beaches in tropical China. Methods: Totally 259 strains were isolated from the rectal swabs of the practitioners and screened by MacConkey agar. A questionnaire survey was conducted. Kirby-Bauer test was used for phenotype, and double disc inhibition synergy test was used for extended-spectrum β -lactamase-producing Enterobacteriaceae (ESBL-E), which was further confirmed by VITEKII instrument. The genotype was detected by polymerase chain reaction, and the similarities of ESBL-E were analyzed using pulsed-field gel electrophoresis. Results: The prevalence of ESBL-E was 13.1% (34/259), of which, CTX-M genes accounted for 44.1% (15/34), mainly CTX-M-14 and CTX-M-27. Moreover, 19.1% (4/21) of the isolates were homologous. The resistance phenotypes of ESBL-E to chloramphenicol, ciprofloxacin, levofloxacin, ceftazidime, cefepime and gentamicin were different between two beaches(P<0.05). The prevalence of ESBL-E was caused by CTX-M genes at the island beach, while a high prevalence of ESBL-E was found at the city beach and clone transfer occurred. Conclusions: ESBL-E-associated gentamicin antibiotic resistance risk may be greater for island beach practitioners. The city beach populations could face more potential risks owing to severe resistance and metastatic ability of ESBL-E. The environmental exposure mechanisms and transfer role of antibiotic resistance at public beaches with high density should be investigated.