Breaks in lines can occur if the line is a sounder-detected bottom and the signal was not clear or bottom detection stopped for some reason. Any line based on a broken sounder-detected bottom line will also have breaks. Breaks can also be created in lines when they are being drawn or if the line status is set to None.
If you are using lines to exclude data for analysis or for creating regions, line breaks may be undesirable. The line-break finding tool can be used to find breaks in a line so you can fill the break in.
To find a break in a line:
Select the line you are checking for breaks from the Line draw tool list 
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Point to a ping that is left of the suspected break.
On the Shortcut menu (right-click), click Find Next Line Break.
Note: If Find Next Line Break is not displayed, no breaks exist to the right of the selected ping
The break points on a line are displayed as blue dots. If the line break is not visible, it is possible that the break is very small – try zooming in (before detecting the break) to see it.
Note: