Are Dolphin Dives faster than swimming?

This article contains a speed comparison of dolphin dives versus swimming and seeks an answer to a fundamental question.  If an entire triathlon swim race were exactly 3.5 feet deep, would it be faster to swim it or push off the bottom and dolphin dive it the whole way?  We all know dolphin dives are helpful as most of the elites are doing them at the start and finish of every swim.  But how much of a difference does it make?  We are very interested in figuring this out.

Dolphin dives are a necessity when the depth is too shallow for swimming, or when your hands start hitting the bottom during the pull.  At such shallow depths, it is impossible to have an optimal freestyle because the bottom is in the way.  For most people, this occurs at depths less than 2.5 feet.  At 3 feet depth, all but the tallest of us can swim normally.  For this reason, we looked at a depth of 3.5 feet, which is deep enough to swim normally but shallow enough to dolphin dive effectively.

I have had many personal racing experiences with dolphin diving, both good and bad.  Early on in my career I was passed at the end of a swim just because my competitors decided to dolphin dive and I didn’t.  This caused me to practice dolphin diving a lot.  On two occasions since, I have been behind at the end of the swim and passed my competitors just because of dolphin diving.  The difference was that I started diving much sooner than anyone else, even when the depth was 6 feet.  So based on this experience, I expected the comparison at 3.5 feet to favor dolphin diving over swimming.

Here’s how the experiment worked.  I swam a total of 8 - 25-yard sprints, as fast as possible.  I took 8 minutes rest between each sprint in order to ensure full recovery.  The swimsuit worn in the experiment was a first model Speedo Fast-Skin.  Each repeat was started by in-water push-off and timed by stopwatch to the hundredth of a second.  Half of the repeats were swimming freestyle, as fast as possible.  The other half were done with dolphin dives, starting from the shallow end of the pool.  At the shallow end, the pool was 3.5 feet deep.  The depth gradually increased, reaching 5 feet depth at 18 yards.  Beyond 18 yards was a sharp drop-off into a deep end of about 10 feet depth.  Thus, each dolphin dive repeat involved 4 dolphin dives, then a push-off and sprint freestyle to the wall for the final 7 yards of the pool.  The freestyle and dolphin dive sprints were alternated.

The experiment has its limitations, so I will point them out for you.  Trying to push off the bottom of a pool is tough.  The bottom was slippery and so I had to push up as much as forward.  Still, I only slipped once through the entire set (dolphin dive repeat number 4), which resulted in a time loss of just 0.3 seconds.  Thus, it would be faster to push off of a surface you can dig your feet into, like sand.  Another limitation is the swimming ability of the test subject (Duane Dobko of Dobkanize.com).  As an experienced swimmer, how my freestyle times related to my dolphin dive times may differ from the average triathlete.  So, it is difficult to know how applicable these results will be for each individual.  The experiment does not look at depths less than 3 feet, which is where most athletes do dolphin dives.  At these depths, it would not be possible to swim freestyle effectively.  Also, there aren’t a lot of 25 yard pools around with a uniform depth less than 3 feet!

The summary data is shown in the figure below.  Results are overwhelmingly in favor of freestyle swimming, and the results were statistically significant.  The difference was 1.3 seconds, or almost 11% of total time.  A gap of over a second in 25 yards is an eternity.  Even if the bottom of the pool was filled with sand, the chances of dolphin dives even matching sprint freestyle are very low.  An interesting observation through this experiment was in the recovery times between each repeat.  It was much easier to recover fully from a dolphin dive repeat compared to a freestyle repeat.  The metric is a soft one as I didn’t have a means of measuring fatigue and recovery but it was very obvious.

How can this be?  The results suggest that dolphin diving has limited value.  And yet, many athletes have won and lost the swim because of their decision to dolphin dive.  But those situations differ dramatically from the experiment.  At the end of an open water swim, you are too tired to swim at maximum speeds.  If it is true that it is easier to recover from a dolphin dive versus swimming, then you should dive when you are tired.  Further analysis is needed to determine what happens to these experiment results when the test subject is tired.  But when you are fresh, deep water dolphin diving is the tortoise and freestyle is the hare. 

Another result in this experiment suggests that shallow water dolphin diving still has merit.  Since dolphin diving means you are continually diving to the bottom as well as moving forward, the distance traveled is greater than freestyle over the same horizontal distance.  If we re-do the analysis with the actual distance traveled versus the horizontal distance of 25 yards, a different picture emerges.  If we assume that a dolphin dive push-off and dive are each at 45 degrees, and 4 dives were taken over 25 yards, and using the same pool depth in this experiment, the total distance travelled is actually 28.3 yards!  This means that the dolphin dive times were slower by 10.8%, but the distance traveled in dolphin dive repeats was 13.2% more than the freestyle repeats.  Thus, dolphin diving is faster than freestyle if the distances are equal, and dolphin dive effectiveness will improve as the water depth decreases.  Although that point where dolphin diving wins could not be determined in this experiment, it is somewhere less than 3.5 feet.

Hopefully, this article enhances your understanding of the benefits and limitations of dolphin diving as it compares to freestyle swimming.  The experiment casts doubt on the effectiveness of dolphin diving in deep water, greater than 3 feet depth at the start of the race when everybody has lots of fuel in the tank.  However, it leaves the possibility that deep water dives are more crucial at the end of an open water swim, when stress and fatigue make fast swimming more difficult.  Also, it suggests that dolphin diving should be more effective in depths of less than 3 feet.  Until next time, happy training