She was right. You couldn’t see it because of the current, but there was a bulge that swelled out for nearly a metre, just below the surface. You’ve got to make sure you land well out from the bank.

The second guy worked his way up a bit higher than Luke had, did a couple of ape-man yells, then dived, too. The girls squealed louder. I opened my mouth, closed it again as he came up, spluttering and laughing.

Luke pulled himself out onto the far bank. He was tall and muscly, just like I want to be. ‘Call that high?’ he shouted to his mate, and began scrambling up the slope again.

‘He shouldn’t—’ Melody started to stand, but I was already wading into the river. ‘I’ll tell him.’ I started swimming across towards the far bank, right under where Luke was getting ready to dive.

He glared down at me. ‘Move, kid.’ ‘Kid?’ Who did he think—

‘Watch out,’ I called. ‘The bank sticks out here. It’s pretty dangerous.’

The girls had started shrieking and squealing again. The other guy was yelling, too. Luke kept glaring. ‘You’ve got three seconds, son.’

I hauled myself along in the water until I was out of his way. He came off the high bank in a perfect dive, while the squeals rose even louder, and knifed into the river. I saw the shape of him jolt sideways as he thumped into the underwater bulge.

I was already swimming towards him as he came to the surface. From where the others were, it probably looked like an ordinary dive, but I could see his eyes staring, his mouth gaping open. He grunted for breath, struggled to stay afloat. As I reached him, he started to go under again.

I grabbed his elbow, shoved him towards the bank. He grabbed a tree root and clung to it, sucked in air, shuddering and jerking. ‘You OK?’ I went. The girls had gone silent; the other guy called out something. ‘You OK?’ I asked again.

He — Luke — pulled himself away from me. ‘Stuff — off!’ He splashed towards the shallows, awkwardly and slowly. The guy was tough; he must have given himself a real whack against the bank, but he was trying not to show it.

He reached the far shore; stood hunched over, looking shaky. One of the girls asked something; he jerked his head at her. After a few seconds, he went ‘C’mon, Jordy, let’s move. This place sucks.’ The second guy stared, then swam across to join him. Luke didn’t look at me. Melody sat silently. Meg was still trying to boss Kahu around.