The latest iPhones can withstand exposure to water pretty well. If you are planning to go diving with one, you will want to invest in a decent diving case though. The Willbox Diving Case is an underwater housing for iPhone 11 Pro Max, iPhone 11 and older models.
This case has cut outs for the cameras, a shutter button and anti-reflection glass for clearer photos under water. Its sealed design prevents your phone from getting damaged. The Willbox diving case is rated to a depth of 15 meters. It is also snowproof and shockproof.[where to get it]