Water walking is a property that allows you to walk over fluid environments without drowning. This affects moats, pools and swamps as well as lava. As fountains and sinks do not cover a complete square, there is no extra effect while water walking for them. The most common source of being able to walk on water is by wearing a pair of water walking boots.
While water walking, you may safely enter water-based squares listed above and not fall in and potentially drown. Additionally, if your water walking boots are fireproof, you can walk across lava, but you will sustain damage unless fire resistant. If attempting to walk on lava and the boots are NOT fireproof, they will burn up and you suffer the effects of the lava as normal.
If you are over water, you can #dip as much as you want, and as non-fountain water sources cannot break or release monsters, this is relatively safe. Sea monsters (;) become more of a threat to players water walking, however, as the property doesn't provide protection from their delayed instadeath attacks.