Swansea

Swansea often appears as a grumpy, old man. Initially, he doesn't care for any of his co-workers, and often loses his temper with his intern Daisuke, whom he often finds to be more of a nuisance than anything else. He continuously blocks off the path to the utility room claiming that it's filled to the brim with foam, which turned out to be a lie as he was trying to hide the only working cryostasis pod from the other crew members.

Although he has a very tough, cold exterior, he did seemingly care for Daisuke; it is implied he was hiding the pod in the hope that Daisuke could use it. Whether cared for the others as much as he cared for Daisuke is unknown.

Swansea is easily irritated, aloof but also quite stoic before the crash, accepting what will happen to Pony Express without worrying or panicking as much as the others. However, after the crash, especially in Jimmy's perspective, he is shown to be extremely violent, incompetent, a drunkard and even "insane". While relapsing may have greatly affected his personality, it can be said Jimmy heavily exaggerated his traits.
(description is from his wiki)

For him we have a very specific idea on how he should sound. A voice simalar to what we want for him is Dave B. Mitchell's character in Lego Monkie Kid Pigsy