Minecraft touch water = death how does it work?

I'm currently building a map in which you should die when you touch the water, it should not give a radius, it should only be the person killed.

now I had some ideas with Execute but nothing works for me in 1.15.

could you help me there and write a command

https://www.minecraftforum.net/...-the-water

execute @a ~ ~ ~ detect ~ ~ ~ minecraft: water 0 / kill @p

That doesn't work for me in 1.15