Everyone knows what guideline reels are for -- right? You use them for cave or wreck penetration; the rest of the time they can spend sitting on the shelf. And, if you are not a cave or wreck diver, you don't even need to own a guideline reel -- correct?
Not quite. The fact is, there are countless uses for guideline reels that go far beyond exploration. Here are some examples:

Instant Search Pattern: Let's say you accidentally drop something to the bottom of the quarry, lake or ocean. Perhaps someone else has done the dropping, and is seeking your help in finding the lost object. Either way, you know from your training that a circular sweep is among the most effective of all search patterns. The catch is, to execute one; you need a guideline and a means of controlling it.
You know where this is leading: If you carry a small reel with you on all dives you are instantly ready to initiate a circular sweep search pattern that can cover over 60,000 square feet of bottom. Not bad.

Advanced Diver Training: Most Advanced Diver courses include an exercise in which students determine the average number of seconds and kick cycles it takes to cover a measured distance (typically 100 feet). What is the best way to quickly establish a course over which students can perform this exercise?
Again, a dive reel is the best solution. Simply mark the guideline at the desired distance. Your measured course can then be set up at a moment's notice.

Dive Floats/Flags: The most common means of controlling the lines leading to dive floats and a flag is a pronged affair that is neither elegant nor easy to use. The next time you need to tow a float or flag, or lead a drift dive, try using a dive reel instead. Once you do, using something more primitive will no longer be an option.

Fly a Kite: Are we kidding? Not at all. The next time the wind comes up, get yourself a kite and use your dive reel to fly it. You'll find that it's a distinct improvement over a ball of string wrapped around a stick.