In the film Edit
In the movie, when Forrest enters the Army bus, Bubba lets Forrest sit by him, and asks him if he's ever been on a shrimping boat, to which Forrest says "no". Bubba says he's been shrimping his whole life, and that his mother also is in the business, and her mother, and her mother. Bubba wants to go into the shrimping business after his time in the Army. He asks Forrest to come into the shrimping business with him as his First Mate and split profits. Forrest agrees.
The next day the rain stops and the soldiers are immediately ambushed by the Vietnamese. Lt. Dan orders the soldiers to pull back and Bubba tells Forrest to run. Forrest does, but soon is all by himself and rushes back to find Bubba. After finding and rescuing Dallas, Tex, Cleveland, and Lt. Dan, Forrest finds Bubba laying down in the grass, having been shot in the chest to which he picks Bubba up and takes him to the river where Lt. Dan and the others are to which Bubba asks Forrest why it all had to happen and also says that he wants to go home, dying shortly afterward.
Forrest fulfills his promise to go into the shrimping business, and becomes very successful. He gives Bubba's share of the profits to Mrs. Blue, making her faint.