It's an above ground job, hasn't been used yet because we needed mats to go underneath it - which have just arrived. He's got all the kit and caboodle to go with it (including a solar cover which he got very excited about), including filters, and a selection of weird looking things I don't think I have the energy to ask about.
I read reviews online which suggested that particular size could take about 23 hours to fill, but once it is filled you don't need to change the water because of the filtration system. I'll report back...
The whole aim is to help our 5 year old with his swimming, which I have no doubt it will do, but it's definitely on the large side.