"Dolphins?" I suggested.

<Dolphins have to surface to breathe,> Cassie said. <And we won't be able to surface in a vein. The only possible morph is shark.>

"Will we be able to breathe in blood?" Jake asked.

<I think so,> Cassie said uneasily. <I vaguely remember hearing some scientist interviewed on NPR once. She said plasma evolved from seawater. Plasma and seawater have the same basic properties.>

<The shark's gonna be hard to control,> Tobias said. <We're surrounded by blood, folks.>

"We have to try," I said. "If Marco dies, so do we. We've got to stop the Helmacrons."

Jake raised his eyebrows at me. "That didn't sound too self-serving."

(...)

I powered my tail, swam rapidly toward the overpowering smell. Sharks can smell one drop of blood in a vast ocean reeking with life. But this smell! So rich, so strong.

I turned tightly. Poked my strange head into a tight opening and pushed through.

A narrow space. A few inches on one side. A few inches on the other. The shark didn't care. Sharks have no fear.

And the smell! So much blood!

I swam with the current, crossing frantically from one side of the confining space to the other. The prey - where was it? I was confused. I should see the prey silhouetted against the sunlight above.

But there was no sunlight.

And the blood was everywhere!

Imagine a drug addict awash in a sea of drugs.

Ax anywhere near a Cinnabon.

The prey is here! the shark brain shouted. It's everywhere! But . . . where?

The shark could hear a low thump, thump. The stomach gurgling. It could see walls sloping above, sloping below. Contracting and expanding ever so slightly.