Message In A Bottle WIP

This is an artwork concept for a married couples retreat for a Christian church. Its not finished yet. I've been staring at it for too long and wanted to get some ideas on how to improve it.

The theme is "Message In A Bottle" and it is going to be held at a resort on a tropical island. The purpose of the retreat is to help married couples work on their marriages from a Biblical standpoint, and to help encourage their relationships with Jesus. One of the activities they will do is write something on a parchment note (like confessed sins, prayers to God for their marriage, etc.) and put them in a bottle and cast them into the ocean.

The "logo" at the top will end up being a little smaller than it is now. And I've left room for text that will contain the retreat info. Mostly I'm just trying to get that floating island to look good. This is a new venture for me, so if you have any suggestions please let me know! Thanks!

Created in Photoshop CS4. All stock images are from shutterstock.com

**EDIT
Thank you for all your helpful suggestions! Here is the finished version: