You may find some of the information in this thread useful in setting up a system to launch in your situation. The seaweed may be the biggest problem. Setting up a little anchored floating platform like
Wetstuff describes could work in your situation, to allow you to launch off your 5th line. You could consider making a Line Tender out of PVC, as described in the post. This would work better in your situation than a Turbo-style-launcher, for unwinding the kite-lines while walking the kite from the platform back toward shore, in order to properly position the kite.
http://kiteforum.com/viewtopic.php?f=1&t=2332235" onclick="window.open(this.href);return false;
Here is another launch technique you may want to consider. I developed this method and the necessary “belay†tool in order to launch from some very difficult places in the Gorge. It worked fine, but demanded some hours of practice, and of course the time and effort to construct the final version of the “Toolâ€. I call the technique the “Driftfly launchâ€, because the kite drifts a little bit and then flys up. The flying up is necessary to shake off the seaweed. A normal drift launch in a bed of seaweed is risky.
http://kiteforum.com/viewtopic.php?f=1& ... t=driftfly" onclick="window.open(this.href);return false;
I presented a description of various versions of the “tool†in the following thread, the version I presently use is shown on page 2:
http://kiteforum.com/viewtopic.php?f=1& ... rab+a+line" onclick="window.open(this.href);return false;
If you get really desperate, then, just before you resort to buying a “launch boatâ€, you might want to consider the possibility of constructing and using the “Pipe launcher†as presented in this thread. This is about as unconventional as you can get:
http://kiteforum.com/viewtopic.php?f=1& ... e+launcher" onclick="window.open(this.href);return false;