GoKawiilIn short: yes, it's generally fine to take your Apple Watch in the water, so long as it's a Series 2 or newer, but the depths you can go vary. All Apple Watches Series 2 and later have a water resistance rating of 50 meters, meaning they're okay for shallow swimming in a pool or ocean. All three Apple Watch SE models the company has released have this rating, as well. All Apple Watch Ultra models, on the other hand, have a rating of 100 meters, making them suitable for more intense activities like water skiing and scuba diving (up to 130 feet).
Besides resistance rating, there are other things to look out for when taking your Apple Watch into the water to make the experience as safe as possible. For one, not all Apple Watch bands, like those made of stainless steel or leather, are suitable for water use. It's also important to note that water resistance doesn't last forever. The longer you've had your Apple Watch, and the more it's been exposed to things like physical damage, soap, and steam can affect how the device handles water.
Apple's Water Lock is another key part of ensuring a perfect swim. It prevents any phantom touches on your screen from the water during a workout, and when deactivated it performs a series of vibrations to knock out any liquid that may have gotten inside. Water lock turns on automatically when you start a water-based workout, or can be turned on manually from the control center. So long as you aren't going deep sea diving, all these considerations will let you use your Apple Watch in the water without a hitch.