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Courtesy of Athlee, a SwimSwam partner
“I know a lot more about swimming now after watching more underwater videos this past year than I have in my entire career.” David Marsh, Olympic Coach.
This was just one of the interesting perspectives in our interview with world-renowned David Marsh. Marsh is a world-class coach currently at Cal Bears, where he focuses on swim technique. Despite having coached more than 50 Olympians, he is still humble about his learning path. Or, as he puts it, “We are just such infective fish”
What You Can’t See from the Deck
Over the past year, Marsh has dived much deeper into underwater video analysis, realizing how much of swimming’s true story lies beneath the surface. As Marsh puts it, “Most technical improvements—about 80%—are discovered through underwater viewing.” This revelation has transformed his perspective, allowing him to uncover nuances in technique that had once eluded him.
“Knowing what brings propulsion is so important,” Marsh said, stressing that underwater feedback allows coaches to see details they could never pick up on otherwise. With a live view from underwater, Marsh now quickly gets insights into crucial perspectives like the swimmer’s rotation, body position, and catch.
“I look at their body, the main part of the body and what it is doing. A lot of times, mistakes are made with the head position and then the hip position. If the kick technique is not synched up with the flow of the stroke, it is obviously a problem.”
Live underwater view in the Athlee app. Photo via Athlee
Marsh emphasizes the importance of mastering the initial grip on the water at the front of the stroke and transitioning it smoothly throughout. He calls this process “dropping the anchor” — a critical technique that requires continuous refinement to generate powerful propulsion.
By observing underwater, coaches and swimmers can much better understand how to maintain this firm hold, make the stroke as efficient as possible, and make immediate targeted adjustments. He stresses that such details “are impossible to see from above the water, but underwater video makes them crystal clear.”
For Marsh, this is also one of the areas of coaching he enjoys the most. “This is the area of the sport that I probably love the most, figuring out how to be more efficient and how to manage the relationship with the water,” said Marsh. This aligns well with Marsh’s belief that coaches should consistently educate themselves and improve their technical understanding through “training your eyes to see what is excellent swimming.”
“I think we in the sport of swimming are very fortunate that we are not natural in the water. To me, there is so much upside to that. We are such inefficient fish as human beings. For us to get just a little bit better, being fish-like can have huge results.”
But what does this mean in real training? Marsh breaks down how he uses underwater video almost daily now.
Today, with Berkeley’s Athlee cameras, underwater video feedback is fully integrated into Marsh’s daily routine with swimmers. The easy setup means that he can just “pop it into the water” to observe swimmers as they train. This allows him to immediately review their technique by watching replays on the spot on his iPad or iPhone.
Marsh explains that rather than recording everything, he often just watches in real-time. For instance, he often watches a full 50-meter lap, replaying the entire swim in 10-second intervals. This enables him to zoom in on critical moments, providing focused feedback that swimmers can instantly apply.
And this is a key point for Marsh.
Instead of overwhelming them with feedback, the swimmers should only be given “a single focus point,” such as refining their kick or adjusting their catch. By doing so, Marsh ensures swimmers aren’t overwhelmed by too many changes at once, allowing them to make targeted improvements.
A swimmer examines his technique on a replay, with Marsh guiding the analysis. Photo via Athlee
One way Marsh maximizes the benefits of video feedback is by encouraging peer learning, which is already built into the culture at Berkeley. He often gathers swimmers to review each other’s videos, and then he pinpoints areas in which one excels, guiding others to replicate those improvements. This collaborative approach helps athletes not only understand their technique better but also learn from their teammates’ strengths.
During his time at Berkeley, Marsh reflects on how underwater video feedback has allowed him to elevate his coaching impact. By turning observations into real-time feedback, he can make immediate improvements in his athletes’ performance. “The Athlee camera has really allowed me to have more impact this year because I’ve been able to take that information quickly and turn it into something of value,” Marsh explains.
Having an impact is, after all, what coaching is all about.
The defining moment for an Olympian
Marsh rounds out the conversation by reflecting on the commonality among all the Olympians he has coached and met: “I have never had an Olympic swimmer who could not point to a particular day or a season where a coach helped them change their mindset and set them on a limitless path.”
Often, that moment happens earlier in a swimmer’s career than you might expect. “They almost always had a coach at a critical time, usually between the ages 11 to 14. In that window, you can really set their mind on fire for the future.”
Marsh’s approach, built on decades of experience and a thirst for continual learning, can remind us that growth is essential for everyone in the sport—swimmers and coaches alike. The impact a coach can have at the right moment is crucial in shaping an athlete’s limitless potential, and guiding them towards success.
The Athlee camera can be positioned anywhere along the pool deck, allowing coaches to capture specific angles for detailed underwater analysis. Photo via Athlee
If you want more information about how you too can get the missing 80%, Athlee can help. Please visit www.athlee.com and book a quick online demo.
Note: David Marsh’s participation in this interview is entirely independent, and he is not compensated by or affiliated with Athlee. The David Marsh interview was conducted by Jeff Grace.