Sydney Whale-Watching Cruise. Cruise the ocean waters off of Sydney to look for humpback and southern right whales as they migrate between Antarctica and the Great Barrier Reef from May to November. Your whale-watching experience starts out of Sydney Harbour and heads to the open ocean on a custom-built catamaran with large viewing windows and spacious decks that provide excellent sightlines. Often, dolphins, sea birds and other marine animals make an appearance during the nearly 2.5-hour whale-watching tour. Book and Save 21%! Sydney Whale-Watching Cruise.