Can I use my apple 7 watch to time my workout in the pool or not?

Correction. While timing a swimming session is an approved activity for Apple Watch, Apple Watch is NOT, nor has it ever been classified as waterproof. It is Water Resistant.

See this link about water resistance for Apple Watch --> About Apple Watch water resistance - Apple Support

Swimming is an activity option so I guess it’s a yes as the watch is waterproof

Your right, mixed the 2

water resistant 😄👍🏼

Apple wouldn't tell you can do so, unless they mean it, Really Really! Don't dive deep, but surface swimming should be fine.