Swim accessories differ from elliptical machines because swim accessories support pool-based skill practice, comfort, and water resistance, while elliptical machines provide dry-land cardio on a guided stride path. One is a set of pool tools; the other is a complete cardio machine.
The difference matters because swim accessories help with swimming technique, body position, breathing, kick, pull, and comfort. Ellipticals are better for convenient low-impact cardio when a pool, lane, or swim skill focus is not part of the session.