Subject: Thank You for the Invite!
Hi Cindy,
Thank you so much for inviting me to go swimming tomorrow at 4:00 PM! I really appreciate it, and I wish I could join you.
Unfortunately, I can't go swimming because I have to help my mom with some chores at home. I’m really sad to miss out on the fun!
However, I would love to go swimming with you another day! How about Saturday at 2:00 PM instead? Let me know if that works for you!
Looking forward to swimming together soon!
Best,
[Your Name]