Is this a real dive watch?

It has dive-watch styling, but no water-resistance depth or ISO 6425 certification is stated. Treat it as a sporty everyday automatic, not a watch for actual diving.

How accurate is the automatic movement?

Movements in this class typically run within roughly 20 to 40 seconds a day. Expect to reset the time every week or two rather than daily.

Does the sapphire crystal matter?

Yes. Sapphire is far more scratch-resistant than mineral glass, which is what most rivals at this level use. It is the standout spec here.

Will it fit a small wrist?

Dive-style cases are usually 40mm or larger and fairly thick. Check the case diameter and lug-to-lug measurement before buying if your wrist is under about 6.5 inches.

What should I compare it with?

Look at Seiko 5 Sports and Orient divers for proven movements and better lume, or Citizen autos. Choose this one if the green dial and sapphire glass matter more than dive credentials.

Does it need winding if I don't wear it daily?

An automatic winds from wrist movement. If you leave it off for a couple of days it will stop, so give it a few shakes or hand-wind it before wearing.