“Seventeen minutes till low tide,” I murmur to Vi, amazed that it’s only been ten minutes since I last looked at my watch. “At that point, there’ll be a bit of time when the water does nothing – they call it ‘slack water’ – and then it’ll be rushing back in here. We have to be gone by then.”

And that’s when we hear it again: the cry of the malamander – a piercing, shrieking, prehistoric sound that echoes through the dripping iron carcass of the battleship.

“That sounds close,” I gasp, clutching Violet’s arm.

“That’s because this is its home,” Vi whispers. “Eels might feel confident while the tide is out, with his harpoons and chain mail. But once this place fills with sea again, I don’t think he’ll stand much chance against a monstrous fish-man.”

“Neither will we,” I want to say, but don’t. What I say instead is, “We should go that way, where the water gets deeper.” And I point. “Somehow, I just know that’s where all the action will be.”

We edge forward, our feet labouring through the deepening water. I reach into my pockets, hoping to feel the last of the warmth of the hot pebbles, but they are as cold now as the metal all around. I dump them in the water and keep wading on. In the light of our torches, I can see we’re approaching a T-junction.

I’m about to make a comment about not losing our way when there’s a gentle, flippery sound somewhere behind us, and a soft throaty clicking.

I freeze and feel Violet do the same. Slowly, we turn, and bring our torches up.

There is something standing at the higher, drier end of the corridor. As our light hits it we catch the gleam of scales, and I think at first it is Sebastian Eels in his chain mail. But then it blinks, the something, with two enormous spotlight eyes, and I know with dread certainty that it’s not Eels. It drops into a low, menacing crouch, and double rows of webbed spines rise up along its back. Two long-fingered claws flex graspingly at us, and a mouth gapes open, edged with teeth like needles.

It’s the malamander.

And it takes a step forward.

I’m just about to shout a very bad word indeed and explode into a million terrified pieces, when Violet does something amazing.

She speaks!

“It’s OK,” she calls out, trying to hide the shock and fear in her voice with a soothing tone. “We’re not here to hurt you. We’re friends, OK? Just friends. We mean you no harm.”

She’s holding her trembling hands out, showing one empty and the other holding the torch beam down.

The malamander stops, and tips its head to one side as if listening. It blinks again.