Let me expalin something, since I always hear this same argument whenever this topic comes up. You can use pretty much any watch out there as a pilot, I know, I used to be one. You can "explore" with any watch that's relatively robust. As for the Speedmaster, don't get me started. Astronauts back in the day and now wear whatever they want, as anybody who has studied the breed knows (NASA made them carry along a Speedmaster even though they failed multiple times on moon missions, and Commander Swigert was clearly wearing his personal GMT Master on Apollo 13). But for diving, which I've been doing for 40 years, you need a dive watch. It is the most function-specific watch made, and is designed and constructed for this purpose. As for dive computers, I use one but in situations where decompression can be an issue I always wear a mechanical dive watch as well for they are far more reliable and computers have been known to fail for all kinds of reasons. They latest computers are brilliant, but the dive watch is far from obsolete just like mechanical altimeters are still there to back up glass cockpits in the latest commercial aircraft. A lot of younger divers have never worn a dive watch as the computer is all they know and they've become totally reliant on them as if they have their Smart Phone with them underwater. A watch is still a very important tool, and in shallower work I don't even take the computer. But the watch always goes with me.
To me using a dive watch as a fashion accessory is like driivng around in a 4X4 pickup when you never, ever need to haul anything much less go off road. I mention this because I'm old enough to remember when only divers wore dive watches, and everybody else wore a whole universe of different timepieces that suited their lifestyle. To get back to the subject: I and my brothers gave my father, a field geologist and petroleum engineer, an Air-King because with it's simple, rugged design it suited him perfectly and he wore it for nearly 40 years. Get your father a watch that suits him, not some timepiece that is all the rage in the "watch community."
