PaperMC/nms-patches/ItemBoat.patch

--- a/net/minecraft/server/ItemBoat.java
+++ b/net/minecraft/server/ItemBoat.java
@@ -41,6 +41,14 @@
             }
 
             if (movingobjectposition.getType() == MovingObjectPosition.EnumMovingObjectType.BLOCK) {
+                // CraftBukkit start - Boat placement
+                MovingObjectPositionBlock movingobjectpositionblock = (MovingObjectPositionBlock) movingobjectposition;
+                org.bukkit.event.player.PlayerInteractEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callPlayerInteractEvent(entityhuman, org.bukkit.event.block.Action.RIGHT_CLICK_BLOCK, movingobjectpositionblock.getBlockPosition(), movingobjectpositionblock.getDirection(), itemstack, enumhand);
+
+                if (event.isCancelled()) {
+                    return new InteractionResultWrapper(EnumInteractionResult.PASS, itemstack);
+                }
+                // CraftBukkit end
                 EntityBoat entityboat = new EntityBoat(world, movingobjectposition.getPos().x, movingobjectposition.getPos().y, movingobjectposition.getPos().z);
 
                 entityboat.setType(this.b);
@@ -49,7 +57,7 @@
                     return new InteractionResultWrapper<>(EnumInteractionResult.FAIL, itemstack);
                 } else {
                     if (!world.isClientSide) {
-                        world.addEntity(entityboat);
+                        if (!world.addEntity(entityboat)) return new InteractionResultWrapper(EnumInteractionResult.PASS, itemstack); // CraftBukkit
                     }
 
                     if (!entityhuman.abilities.canInstantlyBuild) {