As the Doctor neared the broken rock formation, he saw Rose's hand move, and then it was joined by the top of her head. Still, he couldn't tell if she was floating up or surfacing of her own volition. Desperately he hoped that it was the latter.

He reached her in another few strokes, just as the tip of her nose emerged from the water. Her heard her gasp and realized with immeasurable relief that she was alive.

"Rose!" he called, reaching for her hand.

Her fingers curled around his wrist, and she spluttered, "Doc…tor!"

Only her nose and mouth were out of the water, and he could see that she was in danger of slipping back down any moment. Immediately he slid her arm over his shoulders and began to pull her up.

Her face cleared the water by a centimeter or two, and then she cried out. "Ah!"

"Rose, what's wrong?" he asked, moving his hand to support her head, to keep it clear of the water and seaweed.

She was still gasping for breath, and he could see the blue tinge around her lips; she'd been under for at least a minute. He inhaled deeply, instructing his lungs to increase oxygen production, then leaned over to press his mouth against hers. He exhaled gently, filling her lungs with oxygen-rich air.

Her hand gripped at his shoulder, and at first he thought she was struggling, but when he drew back and she exhaled she seemed to understand what he had done. He gave her three more breaths, and finally her respiration became steadier. Her head, however, remained partially submerged. He began to lift it.

She squeaked with pain. "Stuck," she gasped.

"What?"

"Stuck," she repeated, her eyes moving downward. "Somethin'… piece of rock… from the arch…"

Immediately he dove beneath the surface. The water's clarity permitted him to see precisely what the problem was, and it was a troubling one. The rock had broken off in large hunks, and one had fallen against the base of the arch, trapping Rose's leg. She had been in precisely the wrong place at the wrong time.

The Doctor wrapped his hands around the hefty fragment, but it resisted his efforts to move it. He studied the predicament for a few seconds, noting that the rock pressed against the upper half of her leg, from just above the knee to just below the hip. He saw no blood, so there was little chance of a compound fracture, but still there was probably a complete or comminuted fracture in the distal portion of the femur.

He reached down to wrap his fingers around her ankle to check the tibialis posterior pulse. He brushed away a leaf clinging to her foot to feel a weak, thready beat. At least it was present. He resurfaced.

Rose was alert, although she was quite pale. "How bad?" she asked.

"Not so very," he replied with an attempt at a reassuring grin. "I'll have you out in no time."

"Think my leg's broken."

"Probably," he responded honestly. "But I can sort that easily."

"Yeah?"

He gave her shoulder a squeeze. "Yeah. Be back in a bit."

He dove down again and once more attempted to shift the large rock. It refused to budge despite his considerable force of will. He would have to try something else. He swam up to tell her his plan.

Pulling the sonic screwdriver from his pocket, he said, "I can create high-level frequencies that'll break the rock into smaller pieces, but it's going to come apart with a bit of a bang."

"That thing's waterproof?" she asked, her eyes flicking to the small instrument in his hand.

"Of course."

"Figures."

"Rose, listen," he said, trying to keep the urgency out of his tone. "I need to get you out of here soon, because the tide's rising and you're not able to rise with it. I can't think of any other way than this."

"'Kay."

She didn't comprehend fully, didn't see the risk.

He explained hurriedly, "Thing is, there's going to be some force when the rock breaks apart. I'm going to stay in front of you, so you shouldn't be hit by anything, but there's a chance that I might be. If that happens, just get yourself to shore." As an afterthought, he asked, "Your arms aren't injured, are they?"

"Don't think so," she replied rather slowly.

He ran his hands over her shoulders and arms quickly; he felt no abnormalities. Lifting his hands out of the water, he made the necessary adjustments to the sonic screwdriver.

"Doctor," she said, reaching out to grip his arm as some clarity finally came to her, "what'd you mean, you might be hurt?"

"Nothing to worry about," he said quickly. He slid in front of her, pressing his chest against her belly. "Remember, Rose, get to shore, and I'll follow."

He could see that she was about to protest, to question the possibility implied by his words, but the water was getting higher, and there was no time to waste. He cradled her head protectively with his left hand and thrust his right into the water to aim the instrument at the rock.

Her heart hammered against him as she waited. Suddenly he sensed the slight change in mass, and his muscles stiffened instinctively. He felt a low, soft thud at the back of his thigh, and something slammed against his right arm, pushing it away from Rose.

He was pushed forward, impelled beneath the surface. Water rushed into his mouth and nose. The Doctor flailed, feeling Rose slip away from the safety of his grasp.