Is the Invicta Pro Diver 43753 good for swimming?

Yes. It has a screw-down crown and dive-watch water resistance, so swimming and snorkeling are fine. Avoid pressing the crown or bezel underwater and skip deep diving.

How does it compare with a Seiko 5 or Casio Duro?

It has the closest Submariner look of the three and a steel bracelet. The Casio Duro is simpler and the Seiko 5 offers automatic movement, but both are respected for consistent quality control.

Does it have a sapphire crystal?

No. It uses a mineral crystal, which resists knocks but scratches more easily than sapphire. A screen protector or careful wear helps.

What size is the case and will it fit small wrists?

It is a large dive-style case, roughly 43 mm across, so it wears big. Wrists under about 6.5 inches may find it heavy and oversized.

What comes in the box?

The watch on its steel bracelet, a presentation box and paperwork. Extra links for sizing are usually included with the bracelet.

Is it worth it over the automatic Pro Diver models?

The quartz version is cheaper to own and more accurate day to day, with no service needs. The automatic models appeal to buyers who want a mechanical movement and a sweeping seconds hand.