In the book The Witch of Blackbird Pond by Elizabeth George Speare, what is the setting for most of Chapter One?

Most of the first chapter of the book takes place onboard the Dolphin, the ship that Kit takes from Barbados to Wethersfield.  The setting of the book is introduced to us in the first paragraph, where we are told what year it is, where Kit is, and where she is going.

ON A MORNING in mid-April, 1687, the brigantine Dolphin left the open sea, sailed briskly across the Sound to the wide mouth of the Connecticut River and into Saybrook Harbor. Kit Tyler had been on the forecastle deck since daybreak, standing close to the rail, staring hungrily at the first sight of land for five weeks.  (Ch. 1) 

All of this is significant to understanding the book.  First of all, knowing the year is obviously important to appreciating Kit’s situation.  Colonial Connecticut was much different from modern life.  Also, it is significant to know that it is mid-April, meaning that it is just the beginning of spring.  It is still pretty cold.  Kit has not seen land for over a month, and this is clearly a circumstance she is neither used to nor enjoys. 
Kit’s reaction to the first sight of land is also telling. 

She could just make out the row of unimpressive shacks and the Bash of raw new lumber. Her smile was admiring from pure relief. At least this grim place was not her destination, and surely the colony at Wethersfield would prove more inviting. (Ch. 1) 

This tells us that Kit has never been to Connecticut before, and that it is different from what she is used to.  It also tells us a lot about the colony.  Conditions were stark and bleak.  It wasn’t heavily populated, at least not in this part. 
In this chapter, therefore, we learn quite a bit about Kit and the colony of Connecticut before we even get to much plot.  While Kit is still on the ship we learn how different Barbados is from Connecticut, and how different Kit is from the Puritans.  One of the main ways this is illustrated is through Kit jumping in the water for the doll.  The Puritans are shocked.  Kit grew up around water, but in Connecticut it is unheard of for a woman to swim.