This flash sale is already more than half sold out, and beats even the Prime Big Deal Days price from earlier this month.

The Ultra 3 touts 42 hours of battery life, off-grid satellite messaging and the biggest Apple Watch screen to date. It’s also $800. Here’s why I’m still upgrading.

Battery performance is a standout feature of the Ultra 3, catering to users with demanding lifestyles. The watch delivers up ...