Thinking about this watch gift, you probably need to have an idea of what he has and what he likes/wants/needs. Maybe he already has a few divers and doesn't really need another but would really appreciate a Pilots watch (Archimedes/Laco). Or maybe divers are all he wears. Maybe he needs a good every day watch for the office because he only has G-shocks and he's going into the business world. I'd try to pick his brain a little and get some insight into his watch interests. Also consider size. If he's small, you may want to stay around 40mm or less. If he's larger, something 38mm may be too small and you may want to look at 40mm+ or larger.
My personal recommendation is an original Seiko Cocktail time. Its a little dressy, but a fun, stylish watch. Almost everyone likes it, and its niche enough that you won't be guessing diver vs everyday vs pilot vs field vs dress vs.... It's just a fun watch to throw on for dinner/drinks.
Probably around $350-500 online. 40mm so fits most wrists. The strap on it sucks, so I'd suggest getting a third party strap or maybe a mesh bracelet for it. Can probably find something nice for $50 or less.