Open the chest in the river at ( -203, -9, 204 ) /waypoint -203, -9, 204 and take the nautical journal Of Sea, Sails and Slumber from it.
Read (examine) the journal while standing very near the chest in the river.
You must examine the book while very near the chest in order for The Crossing of the Fanged Sea quest to update. Reading the book anywhere else only completes THIS quest and will not update the Crossing quest until you come back to the chest and read the book again. If you don't get an update during this quest, come back and read the book again or go back to Biddy Bobick in EL and read the book in front of him.