It's not intense, it's just deep. And it's a full day, by the time you're done--5:30 a.m. to 5:30 p.m.
Two other dives that day and, if you're with Amigos, lunch and an hour or so to tour the Red-footed Booby Bird Sanctuary after a pretty durn good meal on the island at Half Moon Caye. The other two dives are worth the trip, even if you choose to skip the deep dive at the BH. Many do. The snorkeling, according to the part of my crew who've done it at the BH, is wonderful.
But don't push it. There are lots of good dives just barely offshore that will leave you with plenty of beach (let's say "surface", just for kicks
)time on the island. The dive operators will take great care of you and let you maximize your time.
Trust us all, you'll love it.