+3 for the Blue Planet retractable leash, I'm only a newbie at SUP Foiling and spend around 50% of my time in the water :) but starting to get there.
I first used a normal leggie and was terrible, then went to a calf coil and it was a little better but still not great so I went and picked up a Heavy Duty ION Waist Coil leash and it was good for about 6 weeks until it stretched out and started to get wrapped around the foil quite often after crashing and getting stuck in bigger sets. So I saw the Blue Planet creation and called them, unfortunately it was hard getting onto them a few weeks back so I spoke to some of the local shops and I put this together.
I grabbed a Reel Kiteboard Leash from Surf FX (my local on the GC) then went to a local boatshop and picked up 2 meters of 8mm streach cord and put my own version together for around $120 AU. (I already had the ION waist strap though) and this is THE BEST!!!! I've used it 5-6 times now in varying surf and its amazing, when you fall and the cord wraps around the foil it slowly pulls it around the right way and untangles it and SHAZZAM!! your ready to go again!!! the only downside is, when it runs out of leash it gives you a more aggressive tug as you only have 1200mm of shock cord but I think the Blue Planet version with the larger bungee cord would be a bit better.
The main three things I can suggest is,
1- if you make you attaching cords a dual system and a bit longer you can grab it like a handle if your being hit by whitewater
2- I made my cord 1200mm long from eye to eye and it's perfect (I'm 172 cm tall)
3- I ground off the thumb clip on the attachment as it punched a nice little hole in my board during one of my uncontrolled ejections....