/**
 * Called to update the entity's position/logic.
 */
public void onUpdate()
{
    super.onUpdate();

    if (this.fishPosRotationIncrements > 0)
    {
        //...
    }
    else
    {
        //...

        if (this.inGround)
        {
            // The problem is that inTile is never set
            if (this.worldObj.getBlockState(new BlockPos(this.xTile, this.yTile, this.zTile)).getBlock() == this.inTile)
            {
                ++this.ticksInGround;

                if (this.ticksInGround == 1200)
                {
                    this.setDead();
                }

                return;
            }

            this.inGround = false;
            this.motionX *= (double)(this.rand.nextFloat() * 0.2F);
            this.motionY *= (double)(this.rand.nextFloat() * 0.2F);
            this.motionZ *= (double)(this.rand.nextFloat() * 0.2F);
            this.ticksInGround = 0;
            this.ticksInAir = 0;
        }
        else
        {
            ++this.ticksInAir;
        }
        
        //...
    }
}