A heavily pregnant woman was attacked in broad daylight as she sat with friends in Boston.
The woman, who was nine months pregnant at the time, was sat under the railway bridge on Witham Bank East with a man and a woman on Saturday, June 30.
At about 7.30pm a man, who had been swimming in the River Witham, approached the group and assaulted both of the women.
A second man, who had also been in the river, later approached the group carrying a knife. The group then fled and called the police.
Chief Inspector Deborah Clark said: "This was an attack on a heavily pregnant woman, and the consequences could have been devastating.
“We are appealing for witnesses who may have seen the assault to contact us and to assist in our investigation.”
A 32-year-old local man was arrested on suspicion of assault. He has been released under investigation.
If anyone witnessed the assaults, or has information please get in touch with officers by emailing firstname.lastname@example.org with Incident 449 of June 30 in the subject line or call 101 quoting incident 449 of June 30.