Campaigners from five animal rights groups have staged a protest outside the Sea Life centre in Brighton.
The Sea Life Centre sits at the junction of two main roads
They say two tanks which the centre plans to build at the bottom of steps in the entrance could become a target for drunken revellers in the city.
"This will put the seals and otters housed in these tanks at great risk of attack," a spokesman said.
Sea Life said the mammal pools would help raise awareness of the plight of seal populations in the wild.
The protest groups involved in the demo are Brighton Animal Action, the Bornfree Foundation, International Marine Rescue, the Captive Animal Protection Society, and the Green Party.
They have said they want animal welfare considered when the application is assessed by Brighton councillors.
Papers submitted to Brighton council by Sea Life said the two new features at the centre in Madeira Drive include a common seal pool for 2006 and a penguin facility for 2007.
The report states: "The planned new facilities will encourage many new visitors to the Brighton area and help us to deliver our powerful environmental messages to a greater number of people."
And supporting information given to the planning authority states there will be glass screening that will ensure the animals are not reachable, as well as guard rails.