If you want to take some time out from being on top of the water to finding out what is beneath your boat, then make a stop off at the Sea Life Sydney Aquarium. With 14 different themed zones you will be able to explore the underworld of the sea in detail.
Of course, Sydney does not do things by halves so naturally Sydney Aquarium is one of the largest in the world. You've got plenty of species to choose from - over 700 in fact, and another 13,000 animals to boot. So if you fancy sharks in safety or a few rays to light up your day, Sydney Aquarium has them in the hundreds.
Walking under the ocean through Shark Valley is scary yet spectacular and you need a glimpse of the penguins and dugongs to bring you back from the experience. Just make sure you have plenty of time to fully explore, so when you are back on board you can imagine those fish beneath your feet.