It's a basic lifetime skill. Master it and it will serve you well.
Based on the number of failed attempts we all see on any given day at the marina docks, it seems there has to be some sort of mystical trick to throwing a line. Not really! It's all in practice, and a few simple techniques.
Make a few practice throws to verify the technique below and you'll have a skill that, once learned, is rarely forgotten and provides a lifetime of benefit. Be sure to have the right length and strength of line for the job. Also, don't use line that's too light for the amount of wind, or too heavy to throw.
1. Coil the line in one hand, typically the left hand if you're right-handed (or right hand if you're a lefty). The coils should be long but manageable. You may have to add a little twist as you coil to keep the loops straight and tangle-free.
2. Divide the coils evenly between your hands, being careful not to intermingle the coils. At this point, you should have an even number of coils in each hand with a single run of line joining both.
3. Grab the bitter end of the line between a few fingers of the nonthrowing hand (left for right handers, right for left handers).
You can also belay or secure the bitter end to a cleat prior to throwing the line. Doing so, however, limits where you can position yourself when throwing (you'll have to be near the cleat), and it also reduces the length of the line available for throwing. If you do secure the bitter end, be sure to route the line through any hawseholes or outside of lifelines prior to coiling and preparing to throw. Don't rely on standing on the bitter end. Far too often your foot moves during the process and the line goes overboard.
Pick your target on the dock, i.e., the person you're throwing the line to. Head shots are great during the zombie apocalypse, but not so much when line throwing. Aim a little to the person's left or right so they can catch the line rather than having to dodge it. You can also ask them to extend their arm and try to toss the line over it. Be sure to throw enough line, but not so much that it far overshoots your target.
4. Throw the coils in your dominant hand, then quickly release the coils in your other hand, while holding on to the bitter end. Swing your arm in a nice, wide arc such that when you release the line, your arm is basically pointing toward the person you are throwing to. When throwing in this manner, the weight of the first set of coils will pull or carry the second set of coils.
First, no matter how perfect your line-throwing skills, if the line is too short, the evolution will not end well. You'll find that docklines in the 30- to 40-foot range work best for throwing.
Finally, as with any task, preparation is 90% of the battle. Before doing the deed, take a few seconds to prepare the line coils and properly throw them — you'll be amazed at how much this simple step will improve your line-throwing success rate.