If this is on Earth: water but frothed up with air, or perhaps - carbon dioxide?
If I can somehow arrange to have lots of air mixed in the top layers, and then less and less the further down I go, it should decelerate me slowly and break some of the impact. I don’t know if it could be made enough to survive a fall from height. Then you want the frothing localized or somehow to stop as soon as you fall in, or you’ll sink to the bottom of the frothy water and getting water in your lungs is dangerous so it would be hard to breathe -or better - you are equipped with a robust aqualung or similar with plenty of air to breathe when you jump, to get you to safety afterwards.
You could also have fluids of decreasing density one above the other. But you don’t get liquids that much lower density than water, not enough to make a difference. Apart from liquid helium, density about an eighth of that of water. That’s in another answer already, and is very sci. fi. Also, that would freeze the water, you could have ethane then methane, gases / liquids of decreasing density and freezing point poured at the last minute - and how do you then survive when you return to the surface of the water after your dive, now floating beneath layers of ethane, methane and liquid helium? So I can’t really see where to go with that except by frothing up the liquids again. But you want water you can float on ideally so that takes us back to water. If you are permitted to modify the atmosphere as well, you could arrange to have denser gases to fall through with lower terminal velocity which might help (and again closed system breathing)..
However, if you allow me to pick a location, as you didn’t say where this is, and I can choose anywhere in our solar system, well it’s easy. There’s one obvious place.
Let me pick Titan with an insulated suit (because it is incredibly cold there), and air to breathe (there’s no oxygen in its atmosphere) - but you don’t need a pressure suit because the pressure is the same inside and out. Just heat insulation and air to breathe.
In that case the gravity is only 1.352 m/s² and the atmosphere is higher pressure than Earth’s, 45% higher
It’s oceans are somewhat lower density than water, with a mix of methane and ethane. But you’d survive anyway. Terminal velocity would be very low. A tenth of your terminal velocity on Earth. Calculated here as 6.9 meters per second (about 15 miles per hour): At what g is terminal velocity not terminal? (see answer by Mark Beadles). That’s the same speed you are traveling on Earth if you jump down to the ground from a height of 70 centimeters.
So, I’d choose to fall 2,000 feet into its ethane / methane seas. They would provide a bit more cushioning for the impact. But you don’t really need it and it might be inconvenient to end up under the surface in your spacesuit (you would surely sink). So maybe just try to target a puddle instead, for the purposes of fulfilling the conditions of the question of landing in a liquid :).
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