I'm not sure what book you read, but almost nothing you stated is close to what was contained in the book. Gemma and Ty don't even have a relationship until the very end of the first book. There are no "Earth shattering earthquakes" occurring at any time. This was a previous occurrence and is the reason why they live underwater in the first place. Their friends aren't "trapped" underwater, and they aren't gemma's friends because she has only just met them. Scavenger bots? What are those even. They're never mentioned, and food is grown in kelp gardens and fish farms. There is no apocalypse, no radiation sickness, and no tsunamis either. Please reread the book and understand what is happening. I don't recommend the book for anyone under the age of 12.