Is the GA-B2100 worth it over the standard GA-2100?

The B2100 adds Tough Solar and Bluetooth to the same slim case. If you want to avoid battery changes and like phone-based time sync, it is the better pick. The standard GA-2100 is simpler and uses a conventional battery.

Does it need a battery change?

It runs on Tough Solar, charging from light through the dial. In normal use it should not need routine battery replacement, though a long spell in darkness can drain it.

Is it good for swimming?

Yes. It is rated to 200 m water resistance, which covers swimming and snorkeling. Casio does not rate it for scuba diving.

What does the Bluetooth connection do?

It syncs time with your phone and lets you change settings through the Casio Watches app. It does not show notifications or track workouts.

How does it compare with a smartwatch?

It is a rugged solar watch with basic phone pairing, not a smartwatch. It has no GPS, heart-rate sensor or app screen, but it needs far less charging and is tougher.