Yes, K9 Advantix II is waterproof once it has been applied and absorbed into the skin. This means that your dog can be bathed or swim after the product has had a chance to dry, typically within 24 hours of application. However, it's important to note that excessive bathing or swimming may decrease the product's effectiveness, so it's generally recommended to avoid bathing your dog more than once a week and to wait at least 48 hours after application before allowing your dog to swim or bathe.