Good Start, but....
You have a FANTASTIC idea here! The story is off to a great start. I just have some suggestions.
Read the story now
1. The chapters were too short. I read the whole thing in maybe ten minutes. It seemed like it all belonged in one chapter, not four. I would suggest you put the four chapters together. When you write a chapter, you should focus on certain events, then when something new happens (change of scenery, etc.) you should change chapters. For example, I would put all four together and use Day 1 Stranded as your first chapter. You could even make it longer if you wanted to include Week 1. Because a new day/week brings different events.
2. Too much dialogue. Now, when I say this, I don't mean scrap your dialogue. What I mean is that I felt like I was reading a script. There wasn't much description or story telling between the characters talking.
3. Make it a little more realistic. The characters did not seem realistic in their situations. Most people in the real world would freak out if they were on a capsized ship. And Kate would be struggling with watching her best friend die. If Kate and Becky had been friends for years, then Kate should be a mess with possible PTSD. I would suggests making the characters all have some kind of stress, from this experience. You could use Mona as the "mother figure" meant to keep everyone sane and together and protected.
4. I would scrap the beginning where Kate is the only one left alive. Basically, you've just told us that everyone but Kate has died. I wouldn't tell us that. I would let your readers all get emotionally attached to the characters before you kill them. When you kill off a character, it should always be significant. It should affect the other characters as much if not more than it affects the reader. I would suggest starting the story with what happens during the day the bomb strikes then go into the bomb, the sinking, and everyone finding each other.
Overall, you have a great idea and I don't want you to think I hated it because of my suggestions. I didn't and I will definitely continue to read it. My suggestions are just that, suggestions. You can choose to use them or you can do you. Every author is different. I look forward to reading more of "Seven Adrift!"