There are so many things wrong with this!

A:  Dark Gyarados isn't that good.  Shortly, I will
write an article about this, but it's too lengthy to
post here.

B:  It involves three evolutions, two of which are
Stage Twos, the other of which evolves from MAGIKARP!
Just how lucky do you feel, Dr?  This also brings me
to the last problem...

C:  That deck has only one Blastoise, the focus of the
deck!  And how the heck do you plan to get it out
without any trainers!  Don't you realize half energy
in a deck is bad?  You can only play one per turn, and
since you're only going to have crap pokemon unless
you can somehow keep Magikarp alive long enough to use
Rapid Waterfall Evolution, you won't need that much
energy for your basic wimps a good deck would bump off
in a heartbeat.

Ok, that's about it for now.  Now to write the
Gyarados article before I get flamed.

Xhad