One family managed to get on just three rides in seven hours and another mother estimated there were around 4,000 people in the theme park near Pickering on the day she visited, with no obvious signs of a cap on numbers.
Gavin Johnson was a regular pre-pandemic visitor to the resort with his partner and two sons but was left disappointed with their school holiday trip after spending £120 on tickets.
"It was absolutely horrendous. There was no Covid information, they were shutting rides, there was very little hand sanitiser, many of the stations were broken. We were there from 11am-6pm and got on three rides. It was packed out."
Mr Johnson, from Doncaster, estimates that eight rides were out of commission. Six are listed on the Flamingo Land website as being closed for maintenance.
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"They were breaking down as we were going on them. It just felt like they were trying to make money. It was the busiest I'd ever seen the park and the staff didn't seem to know what to do."
His views were echoed by a mother who paid £130 for four tickets for her daughter's birthday celebration.
Her party arrived at 11am but managed to get on just two rides due to long queues and many of the attractions being closed without explanation before they left at 2.30pm.
The woman, who does not wish to be named, booked the tickets in advance online and says insufficient information was provided for customers regarding potential ride closures, social distancing or restrictions on numbers.
"It was really disappointing, such a poor experience. We knew it would be busy being half-term, but there was no control, and nothing on the website about the rides - were they closed because of Covid or were they just broken? There were queues of up to two hours, and no explanations from the staff. One ride, Velocity, was closed while we were waiting for it.
"It really shocked me how little signage there was, even basic prompts about where the toilets were, and it was absolutely heaving. There was nothing on the website about caps on numbers. When events like Ascot have limited entry, you wonder how can it happen? It felt uncomfortable - the tickets were expensive and money could have been deducted for the main thrill rides not being open."
The woman has submitted a complaint to Flamingo Land but has yet to receive a response.
"I felt so sorry for the staff, there was a long queue for the complaints booth and only one girl working on it. None of them were wearing masks.
"I looked on the Alton Towers website and they had succinct information about the procedures in place there. It just felt like Flamingo Lane were opening for their own gain. This isn't an issue that had suddenly popped up - it has been all over social media and they could have addressed it before half-term. It wasn't a one-off."
Flamingo Land Resort has been contacted for comment.