Now you can do just that.
Ocean Park's new "exploring the aquarium" scheme for teens aged 15 and above lets you get into the tank in small groups. All you need is a diving licence - and you can go swimming with sharks.
Recently I did, too, going for a dive in the park's Grand Aquarium.
My first stop: the large viewing panel - from the inside. It was great fun looking back at visitors; many of them waved and laughed, and I waved back in return.
The tank is home to a friendly and curious zebra shark. It was very interested in a new visitor to its turf: me.
My second stop: the large glass-dome panel overlooking spectators. It was a surreal experience gazing down at people looking up at me, even as I floated around underwater. The massive dome causes a slight warp, twisting images out of shape in the crystal-clear water, which added to the fun.
Schools of fish lingered here and there. They never failed to stay together as they flitted about.
My last stop was the side of the tank. Here I could see everything all at once. What a visual treat that was!
The park's beautiful aquarium serves not only to dazzle visitors but also to educate them. A mission of the aquarium is to help promote the cause of marine conservation. By swimming with the fish, you learn to love and appreciate them.
Following my dive, I spoke to two experts from the Ocean Park Conservation Foundation (OPCF). They told me the OPCF's main goals include supporting research about marine conservation. The foundation also runs programmes where participants can gain first-hand experience in saving the environment.
One such programme is a seahorse-tagging scheme that was launched in 2011. Participants go to various dive spots around Hong Kong to tag seahorses with small bands. Researchers can then track their movement, growth and development patterns to better understand the local seahorse population.
The foundation encourages divers, snorkellers or even swimmers to report any seahorse sightings, along with the pictures they took, if possible. It also works to discourage the use of dried seahorses in traditional medicine.
OPCF staffers work with the government to perform "reef checks" as part of an international programme. Volunteer divers with a passion for marine life set out to explore different sites in Hong Kong. They survey the coral, inspect local species, and look for signs of pollution. The health of corals indicates the general health of marine wildlife in an area.
"What can I do?" you may be asking. A lot, actually. Every little bit you do counts.
When you're out on the beach or swimming in the sea, use eco-friendly sunscreen. Sunscreen's UV block can harm corals and the ecosystems around them.
When you go diving around corals, make sure you don't drag your fins along corals - and damage them.
Consider the types of seafood you eat. Consult the WWF's Sustainable Seafood Guide to help stop the overfishing of threatened species.
And of course, do report any seahorses you see swimming around in the water.
The biggest problem in Hong Kong is not that people are unaware of green issues. It's that they often don't do anything about them. Let's all pull together and save our seas!