Can I use 11 pro in waterpark?

This article (About splash, water, and dust resistance of iPhone 7 and later - Apple Support) describes how the iPhone 11 Pro is IP68 is resistant under laboratory conditions to a depth of up to 4 meters for up to 30 minutes. The article clearly states that the certification tests were performed under controlled conditions and that water damage remains outside the scope of warranty coverage.

Remember that 4 meters (about 17 feet) below the surface exerts about 4 times the pressure on your iPhone at the surface of the water, and that the test was for steady state pressure testing and not the kind of sudden or excessive pressure changes that are easily experienced at a water park.

Also remember that the tests were performed on brand new phones which had never been exposed to daily wear and tear. For example, the test phones likely had their SIM trays inserted exactly one time and extracted zero times at the time of the test. Can you say that about your SIM trray at the time you intend to visit the water park? The test phones also had never experienced any kind of flexing, like insertion into a pocket, a case or a selfie stick clip at the time of the test. Can you say that about your iPhone?

The bottom line is that the IP68 rating is expected to give you the confidence that life's daily splashes, but not necessarily any dunkings, will not kill your precious possession. I recommend that you put your iPhone in a true waterproof case if you intend taking it into the water.

It can't get wet.