I see far too many pools where the depth is the same from one end to the other. Maybe it's only the UK but traditionally you have a shallow end and a deep end. So I start with the floor and basic sides with no deco on yet. Walk the floor and see where the head and/or waist is. I make the floor angled or dipped to suit the head and only a slight angle too so that the head is under water at the deep end. Once sorted I add tiles to the sides, maybe blueish. Different coloured tiles to the walkway (different from the pool sides and bigger tiles maybe) and benches. Ladders in the corners maybe with teleport clicks out of the pool to the sides, top of the ladders. An object with water pouring in maybe, a ring of water where the incoming water hits the surface. Some floating rings that rotate slowly, maybe a floating ball. Make the bottom of the pool have your name in it maybe. Little white or yellow floats at the shallow end for those new to swimming. Seating area for parents or tables and chairs + parasols for a poolside cafe or something. You can customise it as befits your imagination.
I try to imagine in my mind pools I have been to and recreate those. Some are fun pools and some are just for your own property so you might like a name in those at the bottom, where you would not in the fun pools. You need benches, what about poolside lockers? Showers to wash the chlorine off, foot trays with clean water in, before going to the dressing room where the proper washing showers are. Think like you do when you go to a real pool. Diving boards, high or springboards? Scenery through a window, maybe a garden effect, slightly misted windows. Anything that gives you the feeling you'd like to stay longer rather than oh it's another pool and walk on by. Maybe a wave pool with palm trees in and water chutes. A few towns here dumped pools and made these modern wave pools instead. With a deep end for the chutes and a seperate non wave pool that is shallow for those wanting a more relaxed area to swim and paddle in.
NOTE: My nick and image are from a company. That company allows people to use them both as long as they get permission and a licence. I have that and a certificate to prove it.
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