Staff and visitors at the popular beauty spot near Alveley, south of Bridgnorth, were "shocked" and "saddened" to learn the items were missing earlier this month, having recently reopened facilities to the public following forced coronavirus closures.
Police believe the equipment was stolen some time between 5pm on June 30 and 8.30pm on July 1.
Among the items taken was the balancing eels piece of play equipment. The 2x3m long carved wooden eels were only installed last year, proving a huge favourite among visiting families.
Other bits of play equipment were also stolen and the total bill to replace everything taken is about £4,500.
Councillors for the area have condemned the "utterly disgraceful" theft.
Lezley Picton, Shropshire Council’s cabinet member for culture, leisure, waste and communications, said the incident had left her "incredibly saddened".
She said: "Staff have been working so hard to get the play area open safely at Severn Valley Country Park. Our visitors love and value this play equipment, and now the enjoyment of many has been ruined by the selfish people who decided that this play equipment shouldn’t be available for everyone.
“If you have seen or heard of anything suspicious, please report it to the police and help us make sure that those responsible and caught and punished.”
Dave Tremellen, Shropshire Councillor for Highley, said the act was "utterly disgraceful" and that he was "angry beyond words".
The theft has been reported to West Mercia Police, which is now investigating the incident.
Inspector Nikki Roberts said: “It’s believed the theft happened between 5pm on June 30 and 8.30pm on July 1, and we’re asking anyone who may have information that can help with our enquiries to please let us know.”
Anyone with information should contact West Mercia Police on 101 or westmercia.police.uk/tua/tell-us-about/cor/tell-us-about-existing-case-report/, quoting incident reference number 22/55657/20.
Alternatively, contact Crimestoppers anonymously on 0800555111 or crimestoppers-uk.org.