NCIS: "Honor Code" (3.07)

Very good ending.

It's the first time we were introducted to the girl, later known as Gibbs' daughter, Kelly. She wore NIS t-shirt, working on the boat.

"Gibbs is left, alone, watching from the sidelines and we see a flashback of him working on the boat with Zach and then another, older flashback of a younger Gibbs working on a boat with a little girl."
http://www.ncisfanwiki.com/page/3.07+-+Honor+Code