Zhang Tie once again broke through the limits of his speed in the water.
Zhang Tie's speed underwater was powered by the suction channel opened by Castle of Black Iron beneath the water. After the channel drew in the current, the vacuum effect created a reactive pulling force in the seawater. This force came from Castle of Black Iron and was thus entirely controlled by Zhang Tie's spiritual energy. It could be made great or small at will.
Several years ago, when Zhang Tie had first reached the Ewindara Archipelago by sea, he had relied on Castle of Black Iron and the ocean currents to travel more than ten thousand kilometers underwater in three days. At that time, what had limited him was the degree to which his body could withstand the friction of the water. Because of the friction and pressure of the seawater, Zhang Tie had even been able to travel underwater while tempering his body and obtaining Iron Fetus Fruits.
This time, Zhang Tie had become a Knight. A Knight's Heart could control Castle of Black Iron's spatial absorption channel with greater flexibility, while his body's endurance had reached a terrifying level. On top of that, Zhang Tie possessed the Water-Blessed Body, which left all his movements underwater unaffected, as well as Battle Qi protecting his body. Especially under the enhancement of the advanced Swift Movement Technique, his speed in the water completely surpassed his flying speed, reaching a limit that even Zhang Tie had never imagined beforehand.
This limit was likewise the greatest speed his body could currently withstand underwater. Once he reached it, Zhang Tie's protective Battle Qi and physical endurance faced unprecedented challenges and pressure, beyond anything he had imagined.
That challenge and pressure came from something Zhang Tie had never paid attention to