Start off by making a dull blue spike and then duplicate them, resizing and rotating as shown here.
Merge all of those spike layers into one layer. Hold Ctrl and click that layer. Then create a New Layer. Choose a pure blue color (maybe 0078FF) and then use the airbrush to color the ends of the spikes as well as the bottom it. Change the layer mode to Color Dodge.
Then duplicate that layer and change the layer mode to Overlay.
Note: this image doesn't quite have the change that you will see when you do this step, so don't worry if this new layer has more effect.
Deselect and then link all 3 layers and then press Ctrl+E to merge them together (do not merge one at a time because it will turn into a different look).
Here is the part where you must judge for yourself. Use the wave filter and set wavelength to about 90 minimum and 220 maximum. Then keep pressing random until you get an effect that looks smooth and the way you want, i chose this look to the left.
Once you get a good wave effect, duplicate that layer and flip it horizontally. Rotate it a bit and move it like i have done showing to the left.
Now for the super fun part.
Merge those 2 layers you should have together into one layer. Then duplicate that layer. Now do a guassian blur effect to about 10. Set the layer mode to Screen. Then duplicate it about 4 or 5 times and you should come out with a nice looking thing like this.
Ok i bet you guys are wondering "What the hell was all that airbrushing for?" and i have a good reason. While this tutorial doesn't show the exact benefits of airbrushing the tentacles, i can assure you that if done properly (and with a little luck) it can have a really nice end effect like this one below.
Note: This technique takes alot of trial and error, the one to the left took me 6 trys before i got the airbrushing to work properly, and i hope you see how much better it can look.
