Boat get/set (double) occupied acceleration, (double) unoccupied deceleration, (boolean) work on land. Good values to maximize boat utility: 0.6 (fast accel.), 0.99 (no loss of boat), true/false, respectively.

src/main/java/net/minecraft/server/EntityBoat.java

@@ -28,6 +28,9 @@ public class EntityBoat extends Entity {
 
     // CraftBukkit start
     public double maxSpeed = 0.4D;
+    public double occupiedDeceleration = 0.2D;
+    public double unoccupiedDeceleration = -1;
+    public boolean landBoats = false;
 
     @Override
     public void collide(Entity entity) {
@@ -233,9 +236,22 @@ public class EntityBoat extends Entity {
             }
 
             if (this.passenger != null) {
-                this.motX += this.passenger.motX * 0.2D;
-                this.motZ += this.passenger.motZ * 0.2D;
+                this.motX += this.passenger.motX * occupiedDeceleration; // CraftBukkit
+                this.motZ += this.passenger.motZ * occupiedDeceleration; // CraftBukkit
             }
+            // CraftBukkit start - block not in vanilla
+            else if (unoccupiedDeceleration >= 0) {
+                this.motX *= unoccupiedDeceleration;
+                this.motZ *= unoccupiedDeceleration;
+                // Kill lingering speed
+                if (motX <= 0.00001) {
+                    motX = 0;
+                }
+                if (motZ <= 0.00001) {
+                    motZ = 0;
+                }
+            }
+            // CraftBukkit end
 
             // CraftBukkit
             d3 = this.maxSpeed;
@@ -255,7 +271,7 @@ public class EntityBoat extends Entity {
                 this.motZ = d3;
             }
 
-            if (this.onGround) {
+            if (this.onGround && !landBoats) { // CraftBukkit
                 this.motX *= 0.5D;
                 this.motY *= 0.5D;
                 this.motZ *= 0.5D;

src/main/java/org/bukkit/craftbukkit/entity/CraftBoat.java

@@ -22,6 +22,32 @@ public class CraftBoat extends CraftVehicle implements Boat {
         }
     }
 
+    public double getOccupiedDeceleration() {
+        return boat.occupiedDeceleration;
+    }
+
+    public void setOccupiedDeceleration(double speed) {
+        if (speed >= 0D) {
+            boat.occupiedDeceleration = speed;
+        }
+    }
+
+    public double getUnoccupiedDeceleration() {
+        return boat.unoccupiedDeceleration;
+    }
+
+    public void setUnoccupiedDeceleration(double speed) {
+        boat.unoccupiedDeceleration = speed;
+    }
+
+    public boolean getWorkOnLand() {
+        return boat.landBoats;
+    }
+
+    public void setWorkOnLand(boolean workOnLand) {
+        boat.landBoats = workOnLand;
+    }
+
     @Override
     public String toString() {
         return "CraftBoat";