How Long had we had the boat?

"So what's the story with the crocodile?" I asked eagerly.
Howe smiled with just a hint of sheepishness. "Well, Carmel and I were on holiday up in Queensland, at a place called Port Douglas, when we decided"--he saw her about to correct him--"when I decided that it would be fun to hire a boat and go out for a little fishing."
"In a crocodile-infested estuary," Carmel added. She turned to me. "Alan was too cheap to pay for a big boat with a guide so we got a little boat by ourselves. A very little boat." She allowed him to continue.
"So we got this little boat," he went on, with a magnanimous nod in her direction, "with a little outboard motor on it, and we set off across this kind of estuary. The estuary was annoyingly crowded with other boats, but I spotted an inlet, and I thought, 'Oh, we'll try up there.' The inlet turns out to be a river--a really beautiful one. So we go cruising up this river and it's just wonderful, your quintessential tropical paradise--big green river, jungle backdrop, colourful birds flying through the trees. You can imagin it. Best of all, there's not a soul around. We've got it all to ourselves. So we find a nice spot and I cut the engine and we're sitting there with our fishing lines in the water having a nice relaxing time when Carmel points out a kind of muddy bare patch on the bank and we realize it's a crocodile launching place. Couldn't be anything else. Then we notice that there are several of these launching places all along the bank. It starts to dawn on us that maybe this is why there is nobody else up here, because it's infested with crocodiles. Just as we are coming to this significant conclusion there's a splash off to one side, like something heavy going into the water, and then a line in the water moving vaguely towards us."
"Whoa," I said.
"My sentiments exactly, Bryson." He grinned.
"So what did you do?"
"Well, like the good sailor I am, I hopped to the motor to get us out of there. Only the motor wouldn't start. It just would not go."
"Meanwhile," Carmel interjected, "I'm sitting in the back of the boat watching this line coming towards us and saying, 'Alan, the crocodile's coming. It's definitely coming our way. Let's get out of here mate. What do you say?'"
"And I'm pulling on the cord, and pulling and pulling , and the engine is just going putt putt putt pffffft. And all the while the crocodile's coming. Finally, miraculously, the engine catches and we're able to move off. Only we're pointing the wrong direction, so we've got to go up the river, away from where we want to be, in order to turn around. Anyway, after much messing around and crashing into banks and a little affectionate discussion of how we're going to die in a minute and it's all my fault, we get turned around. Only to get out of ther we've got to go towards where the crocodile is."
"So where is the crocodile now?"
"No idea. ther's no sign of him now. He's there somewhere, but we don't know where. He could be right alongside the boat for all we know. The water's so murky you can't see two inches into it. But we do know that sometimes crocodiles go for boats."
"Especially little cheap tinny boats," Carmel said, smiling at him.
Alan grinned happily. "So I throw open the throttle," he went on, "and the boat putters along at about half a mile an hour because it is, I have to admit a very small and cheap boat. We've got to go maybe a quarter of a mile through the crocodile's territory at crawling speed and all the while we're sitting there expecting to feel a bang against the hull and to be tipped into the water. It was a little unnerving."
"Did you know," I said, "that an outboard motor engine, when heard underwater, sounds very like the territorial growl of a male crocodile? That's why crocodiles so often go for small boats apparently."
They looked at me with amazement. It's not often a foreigner gets to scare the crap out of Australian listeners, but I had just read the book, after all.
"I'm so glad I didn't know that at Port Douglas," Carmel said. She gave an expansive shiver.
"But you got back okay, I take it?" I asked.
Alan beamed. "We went down the river, across the estuary, and were out of that boat--and I mean clean out--before it touched the dock." He looked at me with a very pleased and expectant smile. "And how long do you think we'd had the boat out? We had hired it for a half day, bear in mind."
I indicated that I couldn't guess.
Howe leaned toward me, beaming all over. "Twenty-nine minutes," he said with the supremest pride. "Guy told us it was a record."
"That's splendid," I said.
"A proud achievement ofr the Howe family," he added, and you could see that he meant it.