Penn is a supporting character in The Neptune Project and The Neptune Challenge. He's one of the many genetically-modified subjects in the series.
Penn is described to be part Chinese and slightly older than the rest of his friends.
Like the rest of the Project Neptune, he wears a sea suit, which was designed to minimize drag when swimming and protect his skin from dangers like jellyfish stings. Attatched to his feet are diving fins. He was equipped with a sea pack that contained necessities such as food bars, a spear gun, and two gold coins sewn into the pack. Penn also has a utility belt that carries his dive knife.
Penn has proven himself to be incredibly vindictive, such as when he tried to avenge Sara's death by blowing up a Marine Guard vessel. He has also shown his great lack of hindsight when he goes to explode the boat, leading to the death of Kyel and forcing his allies to fight for their lives in a preventable skirmish. Afterwards, he realizes the importance of safety in numbers and the priority of surviving over taking down the regime. From that day on, he strives to contribute more to the group and becomes much more amiable.
He is also quite good with technology, as demonstrated in the Neptune Challenge when he figured out a way to stream music through their ear receivers and the sonar disrupter he and Robry designed that was used in their Sea Rangers tryout.
- Sara: Her death devastated him. Penn was deathly loyal to her, as shown when he argued for her final wishes to be buried on land and the lengths he took to avenge her death. It was obvious how he felt about her, but it wasn't confirmed until the Neptune Promise that she was his girlfriend.
- Telepathy: After the transformation, he gains telepathy. With it, he can communicate with humans and dolphins without having to use his voice. He can also read minds if their mental shields aren't too difficult to surpass, or if they aren't used. The extent of his telepathy is unknown, but it is assumed he has a moderate aptitude in it.
- Underwater-Breathing: His lungs are mostly gill filaments, and after his transformation was activated, he was able to fully breathe underwater.
- Marksman: He's a decent shot, as demonstrated when he killed the giant squid that kept Thom hostage.
- As remarked by him in the Neptune Challenge, Penn cannot cook.