Is the GM2100YRA-8A good for swimming?

Yes. It is rated to 200 meters of water resistance, which covers swimming and snorkeling. Casio advises against pressing the buttons underwater.

How does it differ from a standard resin G-Shock?

The main difference is the metal-covered octagonal bezel, which gives it a dressier look. The core is still a shock-resistant resin case with the same quartz analog-digital setup.

Does it need a battery?

Yes. It runs on a quartz movement powered by a battery, not solar charging, so the battery will need replacing eventually.

Is the display easy to read?

The analog hands are clear, but the small digital window is the weak point. Several owners say it is hard to read at a glance, and the hands can cover it.

The watch on its resin band, along with Casio's usual paperwork and warranty information.

Is it worth choosing over a full steel G-Shock?

It gives the steel-look case at a lighter weight and lower cost than full-metal models. You give up solar power and Bluetooth, which the pricier metal G-Shocks offer.