Really fun technique, although I’m not any good at it! ;D (edit: not my video, just one I saw and tried)
The Noodlers Ahab flex nib or Konrad flex nib work great and they’re more economical than the Wahl or Omas pens. If you like fountain pens and ink you’ll probably enjoy trying this!
I found a picture of what it looks like dry and some info on their blog/site here: Writing on Water
I’m not into the whole fancy pen thing, but that was a very interesting video.
Thanks for sharing.
Awesome, thanks for sharing!
I really like wet-in-wet techniques. You can do something like this with a fountain pen and India Ink, too. India ink kind of breaks up funny when dabbed into a blob of water (rather than just flowing and creating a grey spot) for really neat effects like simulating birch bark.
not any good?! thats beutiful!
Me either. The ones I mentioned are only $20. The ones they used in the video are many times that but the flex nibs I mentioned work well too. The key is to get a flex nib so you can vary the width of the lines with pressure.
I’m not affiliated with these guys but have ordered from them and they have great packing/shipping/service. Ahab pens, Konrad pens.
You would like the urushi techniques used on some fountain pens too I bet! 
That’s not me, just a video I saw and wanted to try. :) I’ve updated the original post.
You bet correctly! Neat stuff. They need to make a 1-minute version, though. 
Yes they do!
Looking forward to trying this new ink ‘Qin Shi Huang’ from Noodler’s. Skip to the end for the ‘reveal’…
That’s cool stuff.
This is another video they did showing the fun of using a flex nib. There’s another video ‘drawing on water’ in their youtube list that’s good too but has explicit lyrics so I didn’t link it. :) I like their works. Good for inspiration!
The picture links to their blog page on the ink and pen. The ink, Black Swan in Australian Roses, is a nice one for the flex pens! I like doing a light wash like they did with it and Zhivago (black and green) ink.
http://www.leighreyes.com/blog/wp-content/uploads/2011/01/P1000329-426x640.jpg
Got around to trying some. Neat ink for sure! A slightly pinkish medium dark red in normal light. Glows well under a black light (UV light). A caveat is that on bright white paper the black light effect is somewhat minimized from the intense glow of the paper itself. Turns out egg shell white works well and tan etc. The cardboard I used didn’t really show the ‘glow’ effect to full effect but it shows at least. If you give it a ‘wash’ like with watercolor, I guess as I don’t do watercolor, it really does a neat black light effect in all the ink, even the lightest shade of the wash!
Normal light:
http://imageshack.us/a/img24/2205/zombiefury.jpg
With black light:
http://imageshack.us/a/img850/6153/zombiefurybl.jpg