The Apple Watch Series 8 devices include the same stronger front crystal component as the Series 7 models, making them more resistant to breakage than earlier Apple Watch models.
The aluminum Apple Watch versions use Ion-X glass to protect the display, whereas the stainless steel and titanium variants use sapphire crystal glass. Sapphire crystal glass is a harder material than Ion-X glass, therefore it has better scratch resistance. This implies sapphire crystal models are more resistant to scratches and normal wear.
All Apple Watch Series 8 models have IP6X dust resistance for usage in situations such as the beach or the desert, as well as WR50 water resistance, rated for immersion in water up to 50 meters deep owing to seals and adhesives. The only point of entrance is the speaker, which requires air to make sound and has been engineered to evacuate water utilizing sound vibrations after exposure to moisture.
The Apple Watch may be used when swimming in the ocean or a pool because it is certified for 50m immersion. It is only suitable for shallow water sports and should not be used for scuba diving, waterskiing or any other activity involving high-velocity water or deep submersion. The Apple Watch Ultra is ideal for certain aquatic sports.

Apple's Apple Watch warranty does not cover water damage, so use caution when submerging the device in water.
Bottom line:
WR50 rating suggests only light swimming, no water sports or much of anything else outside of that and bathing. The water resistance of the Apple Watch makes the mini-computer acceptable for fitness enthusiasts who like lap swimming. This is not the water resistant watch you're looking for if you're an avid pool or ocean frolicker.