To try and answer everyone's questions: Yes, he said "need to learn how to breathe like a scuba diver." Since we were on our way to our SI at a beach, he could have pulled them aside and talked to them discreetly during the SI, but that is not his style. We were sitting on a 28 foot boat with the 2 hoovers on one side, along with a senior citizen diver who was very good, and me and my buddy on the other side. We couldn't help but hear him as it made no effort to keep his voice down.
With this dive operation, the DMs are using long hoses and will share their gas with a hoover rather than making the entire group surface ahead of schedule. The DM had to share his air with both of them during the dives. To me that is an incentive to try and improve you air consumption in and of itself.
This DM/guide/instructor is a very good diver and not just a dive guide. He's a PADI Master Diver Instructor, certified full cave diver, and a TDI instructor. He's also very strict and if you do something that displeases him, he makes this gesture of clutching his head as if he were pulling his hair out.
Put a fin in the sand and you'll get a hair-pull. He is also a self-professed "mother hen" and the highest compliment is for him not to ask you for your tank pressure.
When I first dived with him - almost 2 years ago - I didn't care for him at all. I got a few hair-pulls, but didn't have to share air. But now that I have gotten to know him, I like him a lot. He really helped me improve my diving by example and by getting rid of excess lead. I had a problem initially with air trapping in my BC and he would signal me when he saw any bubbles left after venting for the safety stop. He also took me on progressively challenging dives while always being right there in case I had a problem.
The last dive we did with the 2 hoovers was Punta Sur and they managed 120 feet almost without incident. One of them kicked in the face in devil's throat and I lost my reg, but thankfully my mask was under my hood and I didn't lose it. Wasn't too bad.
He will improve you diving while stretching you limits. On the other hand, he is very blunt and I'm sure he alienates divers as well.
And yes, I always give him a big tip. He's not your average DM/guide.