For most of my paddling in a sea kayak I use a leash for my paddle.
I understand that there are numerous paddlers that see no use for one and might deem it dangerous in some environments.
I regard a paddle leash essential for my outings.
It helps keeping the paddle where it belongs: with the kayak.
Too frequently I see paddlers without a leash having their paddle drift away when assisting others, opening their day hatch or taking a picture.
I have tried many times to store the paddle under the perimeter lines but inevitably for some reason they dislodge and fall in the water.
Often I take pictures from the kayak and occasionally I include the bow in the image: I dislike having the paddle resting under the lines...
I have tried a few styles of paddle leash and the one that really bothered me was the coil type designed for surf boards (ankle strap of Velcro and a bulky plastic coil).
The noise of the constant banging of the plastic coil on the deck annoyed me.
My preferred one is no longer available commercially possibly out of "production" since it was overpriced for something that any child could make at home with very simple materials.
Other leashes I tried lacked a safety quick release.
Admittedly having loose bungee cord close to your body can create a risk of entanglement.
The ability to quickly untie the paddle leash is important to me.
While the leash is firmly attached to the paddle (no sliding of the retention system on the shaft) it can be undone in a split second with just two fingers.
The bungee loop has a small section of rope or tape attached allowing for a quick release.
I just grab the "pull tab" and with little effort release the leash.
The leash will not come loose if just yanked on it; I must pull the release tab.
The bungee can be cut to any length ( I make sure mine is long enough to allow layback rolling or stern ruddering).
The materials for this inexpensive leash can be purchased at marine chandlers: all I need is about 2 mt of 5mm bungee, a small plastic tie ball , and a bit of cord.
Getting the right length of the loop is a bit of trial and error but within minutes I work out the right size for the shaft/loom of my paddles.
A bit of tension is needed on the loop when it's attached to the paddle or it just falls off.
The other end of the bungee is attached to the deck of the kayak.
I use the leash on most paddles, for me it's just so convenient not to have to worry about stowing your paddle when both hands are needed on deck.
I remove the leash when I roll play/practice since it interferes with some moves.