Onyx M-16 Manual Inflatable Belt Pack, U.S. Coast Guard Approved, Low Profile, Compact Design, Approved for Users 16 Years and Older; and Over 80 pounds

Seconding this. The belt-worn inflatable ones are awesome. You forget it's there almost immediately after putting it on. I say this as a strong swimmer and adrenaline junkie, there's absolutely no excuse not to wear one and risk your life. Two models I own and can recommend. Both are USCG approved Type V with Type III performance: https://a.co/d/0dgU6fEt https://www.boteboard.com/products/bote-inflatable-belt-pfd