He had logged 25 dives up to then, mostly in springs and a couple of cave dives.
Which ceratinly may put him at a disadvantage on boat dives. I feel fortunate that my OW checkouts were done from a boat. A lot of our student divers do quarry checkouts. While the dives meet the standards, the divers miss something, and later find that out when they do their first boat dive.
Wore a 5mm Farmer John and 5mm shorty in Keys water. (You can figure the lead he carried.)
Something else that we supposedly 'go over' in OW, but probably need to add greater emphasis to, is the need to obtain local information before diving. While something beyond 3mm is possibly appropiate for the supposedly warm water of the Keys, this diver's suit does sound like a bit much for the environment, and I suspect he never thought to call ahead. I was in Islamorada weekend before last, on the Duane and the SG. The water temp down to about 50 feet was 77. Passed through a thermocline at 50 that dropped it to 75. At about 90 feet, right as I approached the deck of the Duane, I passed through another one and it dropped to 72. In a 3mm full suit and a Microprene hooded vest, I was pretty cold as I started my swim around the deck. Warmed up with the swim, but felt it at first. The seas were 4-6 and there were quite a few folks on the boat feeding the fish, including one of my dive buddies.
Had trouble hooking up his regs correctly, couldn't figure out the giant stride, had a hell of a time getting his BC on and fins off and onto the boat. NO buoyancy control. Puked after both dives. Swam with his arms mostly and used up air like a steam engine.
Wish I could say that all my dives therse days were pretty. I actually find that spending a lot of recent time in tec training in some ways has been detrimental, because I go out on boats on coastal dives less frequently than before. On our Keys trip, I did a real nice face plant, instead of a giant stride, on one dive (my excuse was the pitching boat and the weight of the double 120s on my back, not my own clumsiness, of course). The ladder on the boat we were on was 'enclosed' (i.e. the outer ends of the rungs were connected not just a vertical center post (which I find more challenging anyway). The mates made it clear that the best way to ascend the ladder was to take the fins off in the water - perfectly appropriate, even if inconvenient. But, another one of my dive buddies (DM, several hundred dives, lots of coastal / boat experience) lost a fin when he took it off and draped the spring strap over his arm, and one end of the strap came unhooked and the fin disappeared in the current before he could grab it. We all have days of thunder, and days of thuds, I guess.