Two days later, Zhang Hainuo's body finally regained its usual vigor, and with everyone's joint efforts, the repairs on U-21 were successfully completed. The crew then loaded torpedoes, ammunition, and various supplies onto the submarine, and after receiving approval from superiors, U-21 set sail once again.
After these two days of being together, Zhang Hainuo found that although Hesen always had a cold expression, he was actually quite kind-hearted. He never yelled at the sailors, and even his reprimands were rare. His 25 crew members were skilled and coordinated in their work, and they often couldn't resist teasing each other, making the atmosphere here much livelier than on the Sedlitz. Jokes among the crew involved everyone on board, including Captain Hesen and Zhang Hainuo. Surprisingly, Hesen never seemed to mind, while Zhang Hainuo, although a bit uncomfortable at first, quickly adapted.
With the morning sun shining, U-21 slowly left its berth and embarked on a new journey. Standing on the submarine's conning tower and watching the crew tidy up ropes and inspect the waterproof canvas on the submarine guns and machine guns on the fore and aft decks, Zhang Hainuo felt like he was back on the Sedlitz. However, looking at the surrounding docks, buildings, and patrol boats and barges also preparing to set sail, Zhang Hainuo felt like he was standing at the lowest point of the world, a feeling completely different from standing on the bridge of the Sedlitz, gazing out over the sea...
The northern Adriatic Sea was calm. Shortly after leaving Pula, U-21 began its first high-speed run after repairs. When the two 788-horsepower diesel engines were powered up to full throttle, the submarine moved like a swift swordfish darting through the water, plunging its bow into the sea and then rising high, the sawtooth cutter mounted above the bow acting as its blade, a deadly weapon against any unarmored vessel foolish enough to cross its path. However, its primary purpose was to cut through anti-submarine nets. Zhang Hainuo asked other crew members, and even the reputed "madman" Hesen never used it against surface ships.
"Highest speed, 15.8 knots!" finally came the report from the chief mate, Wolf. Zhang Hainuo knew that this speed was quite fast among submarines of various countries, but compared to surface vessels, especially destroyers and torpedo boats with speeds exceeding 30 knots, it seemed somewhat inadequate.
"Submerge in 5 minutes. All compartments, check equipment status!"
After issuing this order through the intercom to the crew inside the submarine, Hesen turned to Zhang Hainuo standing behind him.
"First time diving?"
Zhang Hainuo honestly answered, "Yes." Although they had been on submarines at the Kiel Naval School, they had never accompanied one on a combat mission at sea, making this Zhang Hainuo's first time aboard a submarine setting out for war.
"Don't pray to God when you're down there!" Hesen winked at him.
"Why?" Zhang Hainuo was puzzled. Did praying underwater fall under the jurisdiction of another deity? Poseidon, perhaps?
Hesen explained to Zhang Hainuo that despite the numerous dives U-21 had made since its commissioning, there could be no room for error each time. This was especially true for the first dive after repairs, when any remaining flaws had to be identified and rectified. Otherwise, regret would come knocking when facing the enemy.
Zhang Hainuo took these words to heart. He knew that some things could never be learned in a classroom, and mastering as many skills as possible would be invaluable in wartime.
As the alarm bells for diving sounded, the crew quickly returned to the submarine through the watertight doors on the deck and conning tower. Bubbles began to rise from the bow, stern, and both sides of the submarine, and soon the bow began to be submerged. At this moment, Hesen told Zhang Hainuo, "I'll go down first. You close the hatch!"
Before Zhang Hainuo could say anything, Hesen swiftly slid down the ladder in the passage into the submarine.
"I've only seen an instructor simulate using a removed watertight hatch during training..." Zhang Hainuo held back his thoughts because the submarine was still diving. If he didn't enter the submarine and close the hatch in time, the entire submarine could sink due to this small "mistake," claiming the lives of all twenty-seven crew members, including Zhang Hainuo.
With no other choice, Zhang Hainuo climbed down the ladder and, when his body was fully inside the vertical passage, used his hand to turn the hatch handle to the correct position, pressed down the spring latch on the hatch cover, and continued to stare at the hatch until the seawater completely covered it without seeping in. Only then did he breathe a sigh of relief.
When Zhang Hainuo returned to the cabin, he found Hesen standing there, looking at him with a smile that seemed to say, "You're a madman indeed!" In Zhang Hainuo's mind, it was indeed a bit mad to entrust such an important task to a complete novice like himself. However, on second thought, he believed that after this exercise, even if he suffered amnesia, he would never forget how to close a submarine's watertight hatch—it had become ingrained in his mind and body!
As the submarine submerged to a depth of 35 meters according to the depth gauge, Hesen shouted, "Stop!" After waiting for about 5 minutes, when each compartment—torpedo room, control room, engine room, motor room, and battery compartment—reported no abnormalities, he ordered the submarine to surface to a depth of 10 meters from the sea surface and continue cruising at 5 knots.
Time passed, and Zhang Hainuo gradually felt the air inside the submarine becoming slightly stale. However, it only carried a faint smell of diesel, rather than the various unpleasant and suffocating odors rumored to be present. Nevertheless, for Zhang Hainuo, who had just begun submarine life, this smell made his stomach churn. For the first half-hour, he managed to endure it, but after about forty-five minutes, he began to feel somewhat unable to hold on.
"Odis, get my aromatic vinegar!" Hesen grabbed Zhang Hainuo, who was about to run to the toilet.
Seeing Odis agilely moving between compartments, Zhang Hainuo finally understood why Hesen had chosen such a character as his steward.
What Odis brought was a small metal bottle about the same size and shape as a bottle of aromatic vinegar. When the cork was opened, a strong smell of aromatic vinegar rushed out and quickly spread in the air.
"Oh, another poor child is about to receive the punishment of Poseidon!" Since the submarine submerged, communication officer Frank Langkamp, who had been idle all this time, finally found someone to tease. When Zhang Hainuo looked at him in confusion, the guy made a very painful expression, as if the bottle contained poison rather than aromatic vinegar.
"Here, rub this kind of medicinal vinegar on your temples, nostrils, and the sides of your throat yourself!" Hesen maintained his serious demeanor as he instructed Zhang Hainuo. Zhang Hainuo looked at him, then glanced at the communication officer who had put on another playful expression. Eventually, he followed Hesen's instructions and applied the somewhat unpleasant medicinal vinegar on himself.
Although Zhang Hainuo didn't believe in miraculous remedies, Hesen's potion indeed took effect quickly. Despite the strange scent making him wrinkle his brow repeatedly, his stomach felt relieved from discomfort. After a while, even the detestable seasickness was significantly alleviated.
"It's a traditional secret recipe from the Hesen family. From now on, whenever you feel seasick, get injured, or bruised, you can come to Captain Hesen. It's only one mark each time!" Frank Langkamp joked with a smile. "Consider this a trial, free of charge!"
Hesen, on the other hand, simply smiled without making any comments.
Ten minutes later, U21 smoothly surfaced. Zhang Hainuo soon realized that for the crew, every dive was a torment. Underwater, dangers lurked constantly, and the cramped space and stifling air made it hard to maintain a good mood. At such times, silly or abrupt jokes served as the best outlets and mood boosters.
Over the next two days, U21 spent most of its time navigating on the surface of the sea. When the sea conditions were favorable, its speed could reach 15 knots, but sometimes it could only bump along at 10 knots. Thus, from the port of Pula in the Austro-Hungarian Empire to the mouth of the Adriatic Sea, it took a full two days and nights of sailing before the prey on the surface began to increase gradually after passing the "heel" of the Italian Peninsula.
This time, Hesen decided to head to the waters near the island of Malta because it was not only the busiest maritime route in the Mediterranean but also where British and French vessels frequented the most. Compared to other German submarine captains, Hesen's most notable trait was his love for fishing, especially for big catches.