Duck was relaxing with the Westward fountain while children jumped in and out of the fountain. While running around and playing in her orbit. They were floating on their back when a really young child climbed onto them. Quack held the child to steady them as they sat on her belly.  Children chattered and would occasionally run up to the edge of the fountain and ask questions. 

"Do you feel wet even though you're a merperson?"

"Yup, I like feeling wet."

"Are your scales rough?"

"Only if you touch them the wrong way the other way they feel smooth or slimy."

She flopped her tail over the edge of the fountain and let some of the children touch her scales. Then came the question that set forth the most grueling event Quack has ever endured. 

"Can you swim all day long? With no break to anything?"

The child that was using her as a flotation device looked at her expectantly. Quack pondered before lifting up the child and setting them down on the ground. 

"I'm not sure cause I didn't live in the water like other merfolk sometimes do. So there is only one way to find out."

Getting up she looked around and trying to find a body of water that would be big enough to swim around for 24-hours. They found a nice river area where waterfront properties were. The gaggle of children were following along and watched Quack go into the river. It was then Quack realized something very important and looked back to the children.

"I don't know what time it is and I also forgot to eat before I got in."

The children laughed at her before running off and coming back with fruits and scraps and throwing them in for their friend. Quack laughed, ate some fruit, and did some tricks in the water for the children as thanks. Soon it got dark and the children had to go home. Which left Ducky a little lonely, however they were nothing if not a person of their word. So as their legs and tail burned they pushed on. Their thighs burned and it was all they could think about because they were also bored as there wasn't a whole lot of activities in the river. 

It had been a few hours and Quack was starting to feel somewhat waterlogged. She swirled around and played with a few of her apple cores. Wondering how she was going to be able to get through the rest of the time. How foolish poor Duck had been so very foolish. You see they were tops 4-5 hours into their challenge they had somewhere near 20 more hours to go. Again with no breaks. So blissfully unaware Quack went on not knowing what she had really signed up for. 

By hour 7 their legs felt like jelly but they figured it wasn't too bad that is if they weren't accounting for the odd cottonmouth they had. It was as time went on the more dehydrated they got even though it felt like their body was bloating with water. Hour 9 was filled with shivers as it got into the night and the temperature dropped.  Though it did nothing for her dehydration dilemma her eyes grew sandy and her tongue felt like sand paper no matter how often she dipped it into the water. 10 was when the drowsiness started their eye lids drooped and they would slowly sink under the water. Only to start awake and begin to tread water again. 11 was when things began to get, odd. The water ripples began to make faces at her and she could've sworn that she heard whispering. They couldn't even feel the exhaustion of their body as they were busy fighting with water about, everything, and nothing. 1 am came around and Quack was competing with the water to see who could hold their breath the longest underwater, seemingly forgetting they have no problem breathing underwater. 

This behavior gradually escalated as time went on them staying in the water the entire time. That was until the children found her the next day. Duck had been found face down on the shore their legs kicking in the air as if they were still swimming though their eyes had been closed and they were snoring softly. Quickly children scrambled for adults and Ducky was rushed to a medical center. 

"It's honestly a miracle you lasted so long in a freshwater environment."

"Oh I'm merfolk water is kind of my thing."

"Yes Quack I know, but you're a salt water variety.  What I meant was it's a miracle you were able to live that long in fresh water as the salinity was not high enough for you. Some merfolk can't even breathe in seawater or freshwater if they were not born in them. So, you swimming any number of hours is impressive even if ill advised to say the very least. Your body really held out for you."

"Ohhh.... So what you're saying is my one day freshwater time is basically equivalent to two day seawater. The kids are going to be so impressed!"

The doctor shook their head while Quack scrambled out of the room on their way to tell their friends the exciting development.