ClearAll; hour = Table[i - 1,{i,76}];
tide = {3.9, 3.4, 3.0, 2.8, 3.0, 
         3.6, 4.4, 5.1, 5.7, 6.0, 
         5.6, 4.8, 3.9, 3.4, 2.6, 
         1.9, 1.2, 1.0, 1.3, 2.3, 
         3.2, 4.0, 4.3, 4.5, 4.2, 3.8, 3.3, 3.0, 2.8, 
         3.1, 3.6, 4.5, 5.3, 6.0, 
         6.2, 5.8, 5.1, 4.3, 3.4, 
         2.6, 2.0, 1.6, 1.6, 2.2, 
         3.1, 3.9, 4.5, 4.7, 4.6, 4.2, 3.5, 3.0, 2.6, 
         2.5, 2.8, 3.5, 4.3, 4.9, 
         5.4, 5.5, 5.1, 4.4, 3.5, 
         2.8, 2.2, 1.7, 1.5, 1.8, 
         2.6, 3.4, 4.1, 4.5, 4.5, 4.2, 3.7, 3.1};
data = Map[Thread,Transpose[{hour,tide}]];
lp = ListPlot[data,AxesOrigin->{-2,-0.25},Ticks->{Table[5(i-1),{i,16}],Automatic},
		      AxesLabel->{"t",None},PlotLabel->"Figure 23.1"]