Suunto M-9 Wrist Compass

Q: can I use it for recreational scuba diving?

It's designed to be waterproof, but not to be immersed at depth. Trying to see the compass dial at depth would be difficult if not impossible. I'd get a dedicated scuba compass for that kind of environment.

Q: Is it possible to replace the wristband with a NATO wristband ? How wide is the wristbrand ? Thanks.

Yes, I have it with a NATO strap. Must be 20mm width.

Q: I just want this for just general cardinal direction at a quick glance. Is this good enough, or is it overkill for that purpose?

What is overkill? I have owned SEVERAL button compasses that slip on your watch band, some boasting highly respected name brands. All of them were unreliable. For only thirty dollars, the Suunto M-9 is stable, easy to read, and VERY reliable. The Velcro band may look and feel cheesy, but actually lasts approximately two years of daily active 24/7 use before it must be replaced with a more substantial band. This is the least expensive quality wrist compass on the market. While not intended as a dive compass, mine has been below 90 ft MANY times with no problem.