Motion blur photography captures the chaos of the underwater world by using slow shutter speeds. There are two main flash settings: front curtain sync and rear curtain sync. Front curtain sync fires the flash at the start of the exposure, which is good for tracking moving subjects like sharks. Conversely, rear curtain sync fires at the end, best for unpredictable movements, producing a more natural blur. Ambient light is essential for creating motion; without it, your flash will freeze the subject, eliminating the desired effect.