ðɛɹ bˈɑːdi ʃˈeɪp mˈæksɪmˌaɪzd hˈaɪdɹədˌaɪnæmi swˈɪmɪŋ ɪfˈɪʃənsi, æz ðeɪ dˈɪd hæv ɐ ʃˈɑːɹklˈaɪk tˈeɪl flˈuːk.
Their body shape maximised hydrodynamy (swimming efficiency), as they did have a shark-like tail fluke.