Buying the ship in Brimloch Roon is overated.. You can swim everywhere! Save the $ for training and enchantments.
To move fast across the water, tilt your view up above the horizon, press Shift/Forward Arrow keys and add your straffe right or left keys (right/left arrows) to alter direction. This will pop your party above the water and you'll be skimming across the waves on the tips of your toes!
