Apple Watch Series 6 SE

Yes you can swim and the water lock turns on automatically;

Swim with your Apple Watch

Can I go swimming or take a shower with my Apple Watch?

Apple Watch Series 1 and Apple Watch (1st generation) are splash and water resistant, but submerging Apple Watch Series 1 and Apple Watch (1st generation) isn't recommended.

Apple Watch Series 2 and newer may be used for shallow water activities like swimming in a pool or ocean. However, Apple Watch Series 2 and newer shouldn't be used for scuba diving, water skiing, or other activities involving high velocity water or submersion below shallow depth. 

Showering with Apple Watch Series 2 and newer is ok, but we recommend not exposing Apple Watch to soaps, shampoos, conditioners, lotions, and perfumes as they can negatively affect water seals and acoustic membranes. Apple Watch should be cleaned with fresh water and dried with a lint free-cloth if it comes in contact with anything other than fresh water.

Water resistance isn't a permanent condition and may diminish over time. Apple Watch can't be rechecked or resealed for water resistance. The following may affect the water resistance of your Apple Watch and should be avoided:

• Dropping Apple Watch or subjecting it to other impacts.
• Exposing Apple Watch to soap or soapy water (for example, while showering or bathing). 
• Exposing Apple Watch to perfume, solvents, detergent, acids or acidic foods, insect repellent, lotions, sunscreen, oil, or hair dye. 
• Exposing Apple Watch to high-velocity water (for example, while water skiing). 
• Wearing Apple Watch in the sauna or steam room. 

Not all bands are appropriate for water use. For example, the stainless steel and leather bands aren't water resistant and shouldn't be exposed to liquids.