Yellowtail

"Yellowtail" first appears in "Onion Trade." The original character art (posted to the Steven Universe crew's Tumblr ) shows that his name is Yellowtail.

Appearance
Yellowtail is fair-skinned just like his son Onion. He has a light blonde beard and eyebrows, and seems to be wearing a bright yellow rain coat with two white stripes near the bottom, a bright yellow rain hat, and blue rain boots most of the time.

Personality
Yellowtail, like his son, Onion, speaks in a sort of unknown language, as revealed in "Onion Trade". He cares a lot about Onion, but his job as a sailor leaves him with little time to see him. He seems to be pretty kind to others, but carefree as he put a boat inside the car wash in "Steven and the Stevens", despite the fact that it was too big to fit. In an alternated past when Steven told Greg that the boat was fat, he didn't notice the car driving into a telephone post, setting the car wash on fire.

Onion
Yellowtail doesn't see his son that often as he appears to be a sailor but when they do see each other, it appears that they do have a very good father-son relationship.

Greg Universe
Yellowtail and Greg seem to get along well, as Greg was willing to wash his boat in "Steven and the Stevens". Yellowtail was also shown supporting Greg to help him stand in "Ocean Gem" due to Greg's injured foot.

Trivia

 * Yellowtail is named after the fish of the same name.