Data-driven comparison of water quality, facilities, crowd levels, and conditions at Onekahakaha Beach and Carlsmith Beach.
• You have young kids or want calm, family-friendly conditions
• You want lifeguards on duty
• You want a beach that works any time of year
• You want free parking
• You have young kids or want calm, family-friendly conditions
• You prefer fewer crowds and a quieter atmosphere
• You want a beach that works any time of year
• You want free parking
Both Onekahakaha Beach and Carlsmith Beach show similar bacteria risk levels (2.5/5). Neither has a clear water quality advantage based on available data. At both locations, avoid swimming for 72 hours after heavy rain, and always check for active DOH advisories before entering the water.
Key tip: Avoid swimming for 72 hours after heavy rain at any Hawaiʻi beach. See our rain safety guide →
Comparing beaches? These top-rated tours work great with either option.
Tours listed via Viator and GetYourGuide. Safe to Swim Hawaii may earn a commission if you book, at no extra cost to you.
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Hawaii DOH Clean Water Branch — Beach monitoring, water quality advisories. eha-cloud.doh.hawaii.gov
Safe to Swim Hawaii — Risk ratings based on DOH data, site characteristics, stream proximity, and advisory history. safetoswimhawaii.com
⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with any government agency or monitoring organization. Assessments are based on publicly available data. They are not real-time measurements. “No DOH Alerts” means no advisory is currently posted — it does not mean the water was tested and found clean. DOH only monitors a fraction of Hawaiʻi’s beaches, and some areas have no regular testing at all.
Always verify current conditions with the Hawaii DOH Clean Water Branch before entering the water.
When in doubt, don’t go out.
Free alerts when advisories change at your beach.