Swimming Technique Video Analysis: How to Use Underwater Footage to Identify Your Flaws

Introduction

Swimming is a sport performed underwater, and athletes cannot adjust their movements by looking in a mirror or observing themselves mid-action like runners or cyclists can. Underwater video provides a “spectator’s perspective,” allowing athletes to see what they actually look like while swimming—which often comes as a shock: “I thought I was doing a high-elbow catch, but it turns out my elbow was completely dropped!” This gap between “feeling” and “reality” is a crucial breakthrough point for improving swimming technique.

Underwater Filming Equipment and Setup

Equipment Selection

Equipment Type	Budget Range	Pros and Cons
GoPro waterproof action camera	NT$5,000–15,000	Good image quality, but requires a pool mount
Smartphone + waterproof case	NT$500–2,000	Inexpensive, but waterproof case quality varies greatly
Pool-specific underwater camera rig	NT$2,000–5,000 (including mount)	Fixed angle provides stability, ideal for repeated analysis
Have a teammate hold the camera	Free	Highly flexible, but footage stability is poor

Recommended Filming Angles

Different angles can reveal different technical issues:

• Direct side view (underwater): Observe body horizontal position, kick depth, and arm entry angle
• Direct front view (underwater): Observe left-right symmetry of the pull and entry width
• Direct rear view (underwater): Observe kick rhythm and leg action
• Above the water (overhead view): Observe stroke rhythm and degree of body snake-like weaving
• Side view (surface): Observe breathing height and head position

Key Observation Checklist

Freestyle Underwater Analysis Focus Points

Entry and Extension:

• Is the hand entry position in front of the shoulder line? Does it cross the midline?
• Is there sufficient forward extension after entry?

Catch Phase:

• Is the elbow higher than the wrist (high-elbow catch)?
• Can the forearm become vertical and press backward after the catch?

Finish of the Pull:

• Does the pull extend fully down to the thigh?
• Is there an outward thumb rotation during the exit?

Body Position:

• Is the waist maintained level?
• Is the hips sinking?
• Does the head position allow the water surface to cut across the middle of the forehead?

Kicking:

• Does the kick originate from the hips?
• Are the ankles relaxed?
• Is the kick depth within a reasonable range (toes no deeper than 35 cm)?

Step-by-Step Video Analysis Method

Step 1: Watch at Normal Speed

First, watch at normal speed to get a feel for the overall rhythm and fluidity, and note any issues you “feel” are present.

Step 2: Slow-Motion Analysis

Use 0.25x speed to analyze frame by frame, focusing on the following moments:

• The instant of hand entry
• The deepest point of the catch
• The completion point of the pull
• The highest point of head rotation during breathing

Step 3: Compare with Reference Footage

Select footage of world-class athletes or top Taiwanese swimmers with a similar build to yours for comparison. YouTube has a wealth of usable material.

Step 4: Prioritize Improvements

A single video analysis usually reveals multiple issues. Recommendations:

• Choose only 1–2 of the most critical issues to improve first
• Prioritize issues that cause the greatest loss of speed
• Do not attempt to fix too many things at once, or your movement coordination may break down

Underwater Filming Resources in Taiwan

• National Sports Training Center (Zuoying): Equipped with a professional underwater camera system, available for national team and development squad athletes
• University swim teams: Some schools (such as NTU, NTNU, and NSYSU) have underwater filming equipment
• Commercial swim clubs: Some high-end swimming instruction organizations offer paid underwater video analysis services
• Self-filming: Using a GoPro mounted on the poolside guardrail is the most common method of self-analysis

Recommended Video Analysis Tools

• Coach’s Eye (App): Professional sports analysis app, supports slow motion and drawing annotations
• Dartfish (Desktop software): Professional grade, commonly used by Taiwan national team coaches
• iMovie / CapCut: Free tools, suitable for basic slow-motion analysis
• YouTube: You can upload videos as “unlisted” for easy sharing with remote coaches

Practical Advice

It is recommended to conduct a systematic underwater video analysis every 4–6 weeks, rather than filming at every practice session. When filming, choose a pace that makes the movements clearly visible (slightly slower than maximum speed); at too high a speed, the details become difficult to discern. Immediately after the analysis, record 2–3 improvement focus points in a notebook or on your phone, and review them before the next practice session, forming a positive cycle of “film → analyze → improve → film again.”

Conclusion

Underwater video is the most powerful self-coaching tool for swimmers. In situations where a professional coach is not available for constant guidance (which is the reality for most amateur swimmers in Taiwan), regular video self-analysis can substitute for a coach’s eyes, giving technical improvement an objective basis rather than relying purely on feel. Make good use of this tool, and your swimming technique will progress with greater direction and a sense of accomplishment.

Related Reading

• Self-Analysis of Swimming on Video: Technical Diagnosis Methods for Above- and Underwater Filming
• Swimming Technique Video Analysis: Using Your Phone to Identify Technical Flaws
• Swimming Video Analysis: Key Observation Points for Above- and Underwater Filming
• Video Training for Swimmers: Practical Applications of Underwater Video Analysis