Crocodiles? On my Omaha? It's more unlikely than you think (as they were on Gold, Juno & Sword). Only Sherman DD's were available for tonk support.
EDIT 2: Murrikans were offered the use of any of the Hobart's Funnies, but they refused all except DD. Lesson learned, they accepted Croc support after the landings, especially in Battle of Brest (hint, hint).