Shipwreck

This is the prologue of the book I'm writing:

Rain battered the windows of the porthole and lightning temporarily illuminated the dark sky. The girl was buried in her mother’s arms while thunder shook the tiny vessel. They were tossed mercilessly upon the tsunamis; each wave brought them closer to capsizing. The overhead cabinets opened and the stored supplies piled onto their heads. Lifejackets landed to their right. The mother quickly put one on her daughter. The lights flickered out as another flash of lightning severed the sky in two.

The boat could handle no more. After a quick succession of gigantic waves, it flipped completely upside down. The girl screamed, the mother held her close and glanced toward the port door. It was already leaking sea water. They needed to get on the top, or rather the bottom, of the boat.

The mother waded through the supplies on the floor. It felt like a nightmare where it was impossible to walk because your legs feel like led. She finally reached the door, and the latch was stuck. After a couple of desperate attempts, it broke off and fell into the rising water at their feet. Frantically she searched for another exit, and her eyes landed on the porthole. She grabbed a piece of wood floating on the water, and gathering the strength and force only possible for a protective mother, she smashed the airtight glass with one blow.

She hugged the whimpering girl close and gave one last kiss, then tearing the lifejacket off, she shoved her out of the window. The girl, terrified and freezing, only just realized what her mother was doing. The lifejacket was thrown out of the window after her as she attempted to help her mother through. But she had already realized the situation. She had just barely fit through the hole without her lifejacket, and she would have been screaming in pain because of the cuts the broken glass gave if it wasn’t for the numbingly cold water. But her mother was too big. She would never make it through.

The girl coughed and spluttered with seawater and tears, subconsciously hearing her mother tell her that the coast guard would be there to save her, if she just held on to the bottom of the boat for long enough. The girl reached out a hand, and the mother grasped it. She whispered one last goodbye to her daughter, and the water enveloped her.

There was no time for the girl to mourn, because the waves dashed her against the boat and threatened to pull her under if she didn’t get on top. But it was nearly impossible. Her hands slipped on the convex underside and she became weaker and weaker with every attempt. Finally, she managed to get her upper body onto the surface, and using the very last of her strength, she propelled the rest of herself on by thrashing her legs in the water. She lay sprawled on the boat as her body gave up. But through her closing eyes, she just saw a huge dark mass silhouetted by a flash of lightning.