Loop closure corrects drift of the vehicle by finding correspondence with previously scanned place. Loop closure will connect previously unconnected part of the map into a loop, correcting accumulated errors.
Loop closure is crucial for minimizing drift during scanning of the object.
If scan lines are planned to have more then 80% overlap, survey pattern is absolutely irrelevant as loop closure will be triggered regularly.
Q: My data did not close properly, or the generated point cloud did not connect with itself.
A: To get proper closure on the point clouds, the recommendation is to continue ROV flight for half of the already completed track. That would mean half of the completed flight path needs to be re-done if we are talking about circular and orbital flight paths.