The two protesters left a banner on one of the cranes
Two men from the group New Fathers 4 Justice (NF4J) have staged a Father's Day protest by climbing cranes dressed as Banana Man and Captain America.
David Hodge and Sean Wheeler scaled the cranes beside Newport Leisure Centre in south Wales at 0700 BST on Sunday to highlight fathers' rights.
Mr Hodge came back down at around 1000 BST and Mr Wheeler followed at 1045 BST and both were arrested by police.
Matthew Starmore from NF4J said both wanted changes in the law.
Mr Hodge, who was dressed as Captain America, had been apart from his three children for 15 years, said Mr Starmore.
"He's not been a part of their growing up and he's gone through a great deal of psychological trauma because of it," he said.
Mr Wheeler broke up with his partner last year and has full access to his son but decided to protest because he feels so strongly that the justice system is unfair, said Mr Starmore.
He said he did not know what they had been arrested for but suspected it was for trespass.
He said both men were taken to Newport central police station.
Gwent Police sent officers to the scene to ensure the safety of the protestors and the public, they said.
Traffic diversions were put into place.