Tie Lines

On a water boundary, a tie line is used so that the figure can be closed.  Just wondering how others do it.

Usually there's a monument on each line that heads to the water boundary, many times on the top bank of the river or lake.

I normally run a tie line from monument to monument for closure, and also show a rough distance along the water boundary (even though the fee usually goes to the CL of a river). 

But I've seen others run many tie lines to various fictitious (calc'ed) points along the water boundary, to form a more or less math'ed approximation of the boundary.  Is this the normal method for most here?