The Oceanarium in Lisbon was opened back in 1998 and it is one of the most amazing oceanariums in the world. Some cities do have aquariums, but this is an oceanarium, making the focus on the big ocean and that is why you can meat for example a Sunfish in the Lisbon oceanarium, something that can only be found like this is a few other places in the world.
The oceanarium is located in the Parques des Nacoes (Nations Park), just by the Vasco da Gama mall and the Telecabine, and it has more than 1,000,000 visitors coming by every single year. The biggest tank in the Oceanarium is filled with more than 5000m3 (which is 5,000,000 litres of water). In this tank you can see sharks, barracudas, rays and moray eels (and of course lots of other fishes).
To get to the Oceanarium you can travel with the metro to the station Oriente, or you can travel with bus 5, 10, 19, 21, 28, 50, 68, 81, 82 or 85 which all stop by Oriente.
The entrance fee to to Oceanarium for adults is 17 Euro, while children from 4-11 years need to pay 11 Euro and children who are 3 years or less can enter for free. The entrance to the Oceanarium is just next to where the Telecabine starts from.