Part of it, he says, is because he runs a family-friendly ride - rather than a thrill-seeking one - cruising slightly slower than some other operators so people can admire the beauty rather than it flashing past their eyes.
There is definitely plenty of beauty to see. Luxmore Jet is the only jet-boat operation with Department of Conservation concessions to work on the Upper Waiau River, home to three Lord of the Rings film locations. It also takes you into Lake Manapouri where views of snowcapped mountains and the national park forest, a World Heritage Area, are simply stunning.
Along the way, Lex explained the history of the area, talked about the filming locations, slowed for the odd spin and stopped in crystal clear water so we could look for trout swimming in the deep pools. He said the Upper Waihau has the highest fish population of any river in the country but added that it "depends on the weather as to whether you can see them or not".
We were in luck and I quickly spotted one swimming by. Another followed, then another.
It's only when we returned to land that Caleb emerged from his slumber: a shame really, given he missed so much, including the fish I knew he would have enjoyed.
Caleb's big adventure - which he had been counting down to for weeks - had started several days earlier with a flight from Auckland to Queenstown.
I had been dreading doing it with a toddler, especially one so excited about going on a plane, but the Air NZ cabin crew were brilliant and seemed happy to help with entertainment and plenty of extra treats including tasty black jet plane lollies.
Once in Queenstown, we hired a car and drove to Te Anau, a town which has plenty of family-friendly activities, from hiring bikes, including the intriguing quadricycle, and playing minigolf plus the easy stroll along the edge of the Lake Te Anau to the free Department of Conservation Wildlife Centre.
There are also glow-worm caves, which require another boat ride, this time on a much larger vessel across Lake Te Anau and then into the caves. It's incredibly dark inside them and Caleb was a bit tentative and clung to us as we ventured underground.
"I want to go back," he said at one point, but hung in there and by the time we reached the glow-worms a few minutes later, he was not only fine but curious about what was going on. In the silence of the ancient caves it was almost eerie to see the tiny glowing blue dots covering the damp walls and ceilings.
When we emerged from the caves our guide, Chantelle Ross, asked Caleb, "How was that?" to which he replied with toddler logic, "Dark".
The trip to see the glow-worms was well worth it, even with young children. On the boat ride back to Te Anau a couple of German tourists, who had taken their 15-month-old daughter into the caves, gushed about the child-friendliness of New Zealand and its attractions.
In Te Anau that appeared particularly true. Everyone seemed keen to make sure children were welcomed and staff at restaurants, like Distinction Luxmore's Bailiez Cafe and Distinction Te Anau's bar and formal dining room, went out of their way to help - even providing toys to keep little ones entertained so adults could enjoy their meals with in peace and quiet.
The only problem, if it can be described as one, that we encountered in Te Anau was the abundance of things to do with toddlers: ironically, we struggled to get Caleb to sleep at night as he was so full of excitement ... pity we couldn't put him back on the Luxmore Jet.
CHECKLIST
Getting there: Fly to Queenstown with Air NZ. See webcarhire.com to find the best deal on car hireage and drive straight to Te Anau.
Where to stay: The Distinction Group has two great places in Te Anau, both family-friendly and with superb restaurants. See teanauhotel.co.nz and distinctionluxmore.co.nz.
What to do:
* Try your hand at minigolf. Hire a bike from Gary and Nancy Barnes of Te Anau Mini Golf Quadricycle & Bike Hire. Call 03 249 7211.
* Visit the Te Anau Glowworm Caves.
* Visit Te Anau Wildlife Centre on the edge of Lake Te Anau.
* Take a spin on the Luxmore Jet.
Elizabeth Binning, Dean Purcell and Caleb visited Te Anau as guests of Distinction Te Anau Hotel and Villas and with the help of Air New Zealand and webcarhire.com.