Is the Stuhrling Depthmaster Heritage worth it?

For a Swiss automatic diver under a few hundred dollars, yes. You get 200m water resistance, a screw-down crown and luminous markers. Expect a basic strap and average accuracy rather than luxury finishing.

How does it compare with a Seiko or Orient diver?

Japanese divers like the Seiko 5 Sports and Orient Kamasu usually cost less and have strong reputations for reliability. The Stuhrling's draw is the Swiss movement label and its dressier dive look.

42mm is a mid-size dive watch and fits most wrists of 6.5 inches and up. On wrists under 6 inches it will look and feel large, especially with the rubber strap.

Yes. It is rated to 200m with a screw-down crown, so swimming and snorkeling are fine. Have the crown screwed down and the seals checked before diving.

Does it need winding?

It is an automatic, so it winds from wrist movement. If you don't wear it for a day or two it will stop, and you'll need to wind it and reset the time and date.