Nice images; you've got enough interest with the foreground elements that the waterfall being centred isn't a huge detractor, but the exposure needs some work. You've got a very challenging situation because of the bright water and very dark rock. The best way to approach this would be as an HDR merge.
If you shot these in RAW, you might try using Photomatix or an equivalent HDR program and create an "HDRi" from that single RAW file (to balance out the exposure) then bump up saturation a bit. I've had that salvage some similar shots that I did.
some filters probably would have helped. im going to hawaii and will be shooting waterfalls, and im taking a polarizer (to cut down reflections) and a neutral density filter to compensate for brithness from long exposure times. nice compositions, just a little too much contrast. try metering off something that is more of a neutral lighting next time.