All good replies, thanks. Just to put your minds at ease, both boys are reasonably experienced (although nothing close to many of the people on this board) and have dived in many different environments around the world. We would never dive without a dive plan and they know what to do if we get separated, although it has never happened so far. The reason for my original question was that our dive site last weekend was a flooded quarry in the UK where a number of objects have been sunk / placed which makes for quite a fun dive. However, with the visibility at around 2 meters I found myself glued to my compass to navigate between features and I thought it would be reassuring for me to have them on a buddy line. I know you can use any kind of static lines but I didn’t fancy a couple of meters of trailing line whilst exploring the features. Anyway, I guess the answer to my original question is no and I thank you time.