Water sounds are great, they are evolutionarily built into us as a ‘positive’ frequency and induce relaxation and happiness
The reason you get fountains and water features in public squares and large lobbies is because they are effectively white noise generators and block out other distracting noise. The sound of coffee machines in cafes works in the same way really – in the ‘before times’ I used to be able to get a surprising amount of focused work done in a cafe waiting to pick up my car from the garage just because the din of the cofffee machine cuts out the outside world.
Often the problem with ‘silence’ isn’t so much that you can’t hear anything its more that you get distracted by stuff you normally can’t hear.
I find when I’m doing quite solitary work TV and radio are are a better background that music / streaming etc. At home I have the TV on with the sound down. Broadcast media has a ‘broadcast clock’ – the hour is broken up by scheduled features. While people tend to moan about the DJ’s banter between the songs it provides a really useful meter to subconsciously measure the day by