code: def plot_drawdown_underwater(returns, ax=None, **kwargs):
      
  
      if ax is None:
          ax = plt.gca()
  
      y_axis_formatter = FuncFormatter(utils.percentage)
      ax.yaxis.set_major_formatter(FuncFormatter(y_axis_formatter))
  
      df_cum_rets = ep.cum_returns(returns, starting_value=1.0)
      running_max = np.maximum.accumulate(df_cum_rets)
      underwater = -100 * ((running_max - df_cum_rets) / running_max)
      (underwater).plot(ax=ax, kind='area', color='coral', alpha=0.7, **kwargs)
      ax.set_ylabel('Drawdown')
      ax.set_title('Underwater plot')
      ax.set_xlabel('')
      return ax
docs: Plots how far underwaterr returns are over time, or plots current
      drawdown vs. date.
  
      Parameters
      ----------
      returns : pd.Series
          Daily returns of the strategy, noncumulative.
           - See full explanation in tears.create_full_tear_sheet.
      ax : matplotlib.Axes, optional
          Axes upon which to plot.
      **kwargs, optional
          Passed to plotting function.
  
      Returns
      -------
      ax : matplotlib.Axes
          The axes that were plotted on.