haʊˈɛvɚ, bˈɜːɹoʊɪŋ θˈiəɹi hæv pɹˈɑːbləm, bɪkˈʌz ɡˈɪl ˈoʊpənɪŋz ɑːɹ plˈeɪst lˈoʊɚ pˈɑːɹt ʌv bˈɑːdi, ɹˈɪskɪŋ sˌʌfəkˈeɪʃən.
However, burrowing theory have problem, because gill openings are placed lower part of body, risking suffocation.