John Hopkins

What is going on here?

Then, as she treads water, Nan glances over to one side, where in the distance she can see the shadowy shape of another whale coming towards them.

Rays of sunlight filter through the murky water as Nan squints through her snorkel mask.

The second whale gets nearer and nearer, and as it does, she clocks something unusual.

Its tail fluke is not moving up and down as a whale should, but swishing from side to side, a slow, menacing motion.

Then Nan's body stiffens as a chill runs down her spine.

That is not a whale.

Nan hangs in the water, heart thudding inside her ribs, staring in horror at the 18-foot predator streaking towards her.

Turns out the danger Nan thought she was dealing with isn't the real danger at all.

Highly territorial and extremely aggressive, tiger sharks are among the most feared species in the ocean.

This one is in attack mode, fins down, body arched, and it has Nan in its sights.

Still, despite the immense danger, she again manages to keep her composure.

Capable of reaching speeds of up to 20 miles an hour, there is no way Nan is going to out swim a tiger shark.

But that doesn't mean she isn't going to try.

She turns.

But just as she's about to start frantically paddling in the direction of the boat, something massive comes up underneath her.

It's the whale.

Just like before, the whale carefully positions Nan on the curve of his head and keeps her balanced there as he swims away from the shark.

Except now there is something different about the whale's demeanor.

His movements change.