One approach is mentioned in The Challenge of Creation, by R'
Natan Slifkin, in footnote 2 on page 277: ... others explained
that the deluge did not cover the entire earth, hence not every
species of animal had to be taken on board; see Rabbi Dovid Tzvi
Hoffman, commentary to Genesis, pp. 140-141; Rabbi Azriel Leib
Rakovsky (disciple of Rav Yaakov Karliner, author of the
Miskenos Yaakov), Shelemah Mishnaso to Berachos 56b, and Rabbi
Gedalyah Nadel, BeToraso Shel Rabbi Gedalyah pp. 116-119. For
further discussion of various approaches to the topic of the
deluge, see Rabbi J. Hertz's "Additional Notes to Genesis" at
the back of The Pentateuch. Here's my translation of the
particularly relevant part of BeToraso Shel Rabbi Gedalyah, from
page 118, which can be found on page 65 of the PDF linked on the
sidebar of this page (paragraph breaks and links mine): "To
destroy all flesh ... which is under the heaven, all that's on
the land will perish" - We've already said that "which is under
the heaven" refers to the he