Balloon releases cause massive damage to wildlife, particularly at sea and should not be allowed. The Marine Conservation Society UK support a ban.The following is taken from their website-

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Balloons are mistaken for food by many species of wildlife, especially turtles.

Once balloons have been eaten they can block digestive systems and cause animals to starve. The string on balloons can also entangle and trap animals.'

It is also a form of littering.