How To: Freedive Knots - Florida Freedivers 

Could you use a double uni knot to combine two lines together instead? That's what I use on my fishing poles to combine braid to mono/fluoro

Could you do a video where you could explain different scenarios/species and how that would determine how you would set up your rigging? Like dyneema vs mono shooting line, what size gun, slip tip vs flopper, etc etc

square knots are not good they can slip even when tied properly. they are too easy to slip. better knot is the sheet bend which is similar and just as easy to undo. and also works for two different size lines. also for a better loop knot use a figure eight instead of a simple overhand-once the overhand comes tight you will have to cut it to remove it. figure eights are easy to tie and untie that's why mountain climbers use them. the bowline is the king !! I have towed large comm. boats hundreds of miles in the ocean and then able to quickly untie the loop knot. I was impressed with the other knot you showed never saw it before but it looks good.