Dear Agent Sydney,
Storm Hunter is a YA adventure fantasy novel about a well-meaning thief who avoids trouble on her home island by stowing away on a passing ship. Unfortunately, it’s a pirate ship.
She fights for her place on board, survives shipwreck and first love, and makes her way home again to find trouble still waiting for her. [Good and clear, but you could use the odd adjective to give me a sense of whether or not the story is exciting or romantic etc.]
This is the first book in a trilogy, and it’s 80,000 words long.
As research for Storm Hunter, I read extensively about historical pirates and spent eleven days on board the Young Endeavour sail training vessel (although I admit I wasn’t a stowaway, and no-one tried to kill me [nice personal detail - and good to mention the research]). I’m sick of reading fantasy books set in Britain, so I designed a more original world. [More nice detail - and I applaud use of the informal 'sick'.] Mine has more sunshine and more beaches, so readers will long to visit it over and over again. [I'm starting to forgive your lack of adjectives at the start.] My fantasy world is based on Indonesia, which I have visited eight times. I also have a strong online presence with thousands of followers. [This last sentence should have a separate para and you should explain what that presence is around - your own personal website? Fan fiction? Slash fiction?]
Three of my books have been recommended by three different assessors since I began writing full-time in 2005. [This won't mean much to most agents or publishers. I'd rather hear about why you're writing in this genre and what titles in the genre you like.]
I welcome editing advice. [No need to mention this yet - wait till we get to know each other better. Because at this stage it sounds like you're asking for editorial advice and there's nothing we love more than the emails from authors saying 'What I really want is for you to give me a detailed editorial report on this manuscript that is not really ready for me to show anyone yet'.]
Overall: pretty good - all the requisite information was there. Try to sound as assured about the story you've written as you do about the reasons why you've not set it in Britain.
What you haven't mentioned: if you've already started writing the second book in the trilogy and, as said above, why you're writing in this genre.