Complex sentence: Belugas are one of the cetaceans most commonly kept in captivity in aquariums and wildlife parks in North America, Europe, and Asia; they are popular with the public due to their colour and expression.
Split into simpler sentences: Belugas are one of the most commonly kept cetaceans in captivity and are housed in aquariums, dolphinariums, and wildlife parks in North America, Europe, and Asia. They are popular with the public due to their colour and expression.