Notice that the disciples' fear did not go away. It changed in the kind and focus, from the cowardly fear of the storm to the reverent fear of the One with the power to calm the storm.
Faith has many antonyms. Fear is one of them.
25.268 δειλός, ή, όν: pertaining to being cowardly—‘cowardly, coward.’ τοῖς δὲ δειλοῖς καὶ ἀπίστοις … τὸ μέρος αὐτῶν ἐν τῇ λίμνῃ τῇ καιομένῃ πυρὶ καὶ θείῳ ‘but for cowards and traitors … the place for them is the lake burning with fire and brimstone’ Re 21:8. In some languages a ‘coward’ is ‘one who always runs’ or ‘one who runs away at nothing.’
Mark 4.41 And they feared exceedingly, and said to one another, “Who can this be, that even the wind and the sea obey Him!”
25.252 φοβέομαιa: (derivative of φόβοςa ‘fear,’ 25.251) to be in a state of fearing—‘to fear, to be afraid.’ καὶ ἀκούσαντες οἱ μαθηταὶ ἔπεσαν ἐπὶ πρόσωπον αὐτῶν καὶ ἐφοβήθησαν σφόδρα ‘when the disciples heard this, they fell face downward and were extremely afraid’ Mt 17:6; καὶ μὴ φοβεῖσθε ἀπὸ τῶν ἀποκτεννόντων τὸ σῶμα ‘and do not fear those who are able to kill the body’ Mt 10:28; ἐφοβοῦντο γὰρ τὸν λαόν, μὴ λιθασθῶσιν ‘they were afraid that the people might stone them’ Ac 5:26.
b Matt. 14:31, 32; Luke 8:25
8 NU Have you still no faith?
 The New King James Version (Nashville: Thomas Nelson, 1982), Mk 4:40.
 Johannes P. Louw and Eugene Albert Nida, Greek-English Lexicon of the New Testament: Based on Semantic Domains (New York: United Bible Societies, 1996), 317.
 The New King James Version (Nashville: Thomas Nelson, 1982), Mk 4:41.
 Johannes P. Louw and Eugene Albert Nida, Greek-English Lexicon of the New Testament: Based on Semantic Domains (New York: United Bible Societies, 1996), 315.