Hello RJ1.
Welcome to the Forum.
In addition to using textures you can also change the colour of areas of water by adjusting the Red, Green and Blue colour controls which you’ll find in the World Menu (F6) in Surveyor.
Below the three colour dials you should see the cloud preview window. To the right of this are three small boxes. These are also switches.
The top two small ones deal with lighting of the scene (top is ambient lighting which alters the colour hue of buildings and other objects, the middle one [Sun] primarily effects the terrain colour). The one at the bottom is the Water Colour Preview box which allows you to change the water colour.
LMB click on that box which will light up the RBG dials which you can rotate to change the water colour.
It's also worth mentioning that clouds, which reflect in the water, can also have an impact on the water colour as can time of day setting although less so than using the RGB dials.
