Rey swerved the submersible to avoid colliding with s-foils that had blown off an X-wing. As she made her way back to the island she'd landed on a few hours prior, Rey had to dodge a multitude of wreckage that had fallen out of the sky. Rey felt her heart sink with the rubble, both Resistance and First Order in origin, that slowly disappeared into the depths below.
"Rey, are you there?" Poe's voice sounded from her comm.
"I'm heading to the command center,"
"Don't go back there," Poe warned. "While the First Order is retreating, a number of ties are bombing some of the buildings, and I wouldn't be surprised if the command center is next. I'll send someone to pick you up wherever you resurface,"
"Affirmative," Then, after a moment, Rey asked "Are Finn, Chewbacca, and R2 back in the Falcon?"
"I think Chewbacca and R2 are, but I haven't heard from Finn since he landed," Poe said. "The fighting has been non-stop up here,"
"I'll see if I can locate him. If he's nearby perhaps he can pick me up or the Resistance can bring us back together," Rey switched the direct channel from Poe to Finn. "Finn, are you there?"
"Rey," he replied with relief in his voice, "Yeah, I'm here. Are you ok?"
"Yes, I left the caverns and am in the submersible. What's your location?"
"I'm in the old pod racing tracks under the command center," Finn said. "The First Order troops are retreating, I'm making my way back to the surface,"
Rey tightened her grip on the steering wheel. "You need to get out of there," she said. "I just spoke with Poe and he mentioned some of the buildings are being bombed by the First Order," Checking the monitor in her cockpit, Rey added "I'll reach the command center in a few minutes. Let's follow each other's homing beacons and then someone from the Resistance can pick us up,"
Docking in one of the underwater hangers, Rey found herself in one of the pod racing tracks. If the situation was less dire, she would have marveled at how thrilling it must be to race in such an arena, flying at top speed in glass enclosed tunnels beneath the surface. But in that moment all she saw were Resistance troops clambering for staircases that lead to the surface while explosions rocked both the building and water in the distance.
Pushing against the crowd, the homing beacon blinked rapidly as Finn approached.
"You made it!" Finn said as he grasped her arms.
"And now we leave,"
The two followed the rush, though keeping up with each other in the crowd was near impossible. "Don't worry about that," Rey told herself as the pressing bodies separated Finn from her sight. "The important thing is we both make it off this planet,"
The soldiers became more frantic as the blasts from above grew louder, right up until one of the explosions cracked the passageway wide open. Water rushed inside, filling the tunnel at an alarming rate as it overtook anything in it's path. As everyone began to float to the top of the corridor, Rey came to the heartbreaking conclusion that she would never make it to the surface alive.
Pulling out the homing beacon that tracked Finn, Rey realized he was closer to the staircase than she. "Maybe I won't make it," she thought, "But Finn and these other soldiers still can,"
Rey closed her eyes as a tear rolled down her cheek, knowing what she had to do and that it would take every ounce of strength to do it.
"Be with me,"
Curling her fingers into a fist, the tunnel's fragmented mixture of metal, steel, and glass curled in on itself, creating a crude yet compact end to seal off any additional water from getting in as Rey was left outside the structure. As the ocean engulfed her senses, Rey reached out to the other half of the tunnel that had been severed by the blast, sealing that section off as well. With the last of her strength, Rey called upon the Force one final time to push any soldiers stranded in the water between the two tunnels to the surface.
"Rey!" The Jedi was barely able to hear Ben call her name as she lost consciousness.

Finn pounded on the twisted metal and glass, shouting even though he knew Rey couldn't hear him. "She saved us all," he thought as he watched her motionless body suspended in the water, "But there's nobody to save her,"
Fumbling with his comm link, Finn was going to make an open call to the Resistance for someone to retrieve his friend, but the communication device had been fractured in the aftermath of the blast, rendering it useless.
"No!" Finn slammed his palms on the glass as Rey began to drift away. He refused to leave just yet; if he did, that would mean she had died alone. So he stood there, praying and watching until she disappeared from view.
Maybe it had been wishful thinking, Finn thought after he'd finally departed, but in those final moments while she was still in sight, he could have sworn he saw someone holding her close.