This is an idea that has evolved over a couple of years. Some times here we troll, and jig flies for trout, and after an hour or two this gets a bit much, even if you are catching them. The first one I made, I used a small funnel, attached with 3 pieces light string, did not work too well, and when it did pop out of the water, it usually tangled around the rod tip.
This one is Mk 4 or 5 and seems about as good as it gets, but I am thinking about another 1" in diameter would not hurt.
What’s it do?
You hook the dog clip on to the rod , second runner from the tip is good - The disc should just skim the water, and as soon as a bit of chop hits the disc it digs in, stretches the bungy cord and the disc gets dragged back, bending the rod tip- as soon as the next chop wave comes by the disc will pop out of the water, releasing the rod tip which rips forward about 1.5', this will be repeated, at a not too regular pattern. The best part is, not the lure speeding forward, I think it’s the 1.5' drop back before it goes on it’s forward run. Laugh - you have to see it to believe the extra dimension you get trolling - I now use braided line, which I think is better, because of it’s ‘no stretch’ characteristics. Put a lure in the water beside the boat, and have a look, you will want to dive in after the lure/fly . I recently removed the lip from a couple of divers and weighted them a bit, this is the most natural, unnatural act I have seen.

They have been laughing me off the lake for about a year, and now they want to know how to make one - the only place they will find out is here, so if you are interested, here’s the menu.

What do you need (see pictures):
Half an hour
1 x dog clip- plastic - NOT steel or brass,( so it does not wear your rod blank through)
1 x Plastic ‘Micro Jet’ sprinkler stem (about 10"-12" long)
1 x “ ” “ ” head (does not matter what size/pattern)
1 x 4" Polycarbonate (or Lexan) disc @ 1mm thick (don’t know equivalent is in inches, maybe 3/32")
2' of fine bungy cord
2 x swivels
2 biggish split rings
1 x wooden dowel (polished)

Tools:
A heat gun
A ‘box cutter’
Drill and 3/8" bits

The hardest bit, I find, is dishing the polycarbonate disc. The Poly needs to be at least 1mm thick, any thinner and it does not form too well, it distorts and flies apart.. Mark the centre and mark out 1 1/2"rad circle, and 2" rad , or whatever you want (the 1 ½" circle for the drain holes in the disc). Slowly drill a hole in the centre the same size as the Micro jet thread (which is your ‘bolt’ to hold the disc on the stem). Find a bolt the same size as the hole in the disc and push through (with a washer) the disc centre hole, and place a nut and washer on the other side- tighten up and place it in a drill press or put your drill in a vice and use this to spin the ‘rough disc’. Get the box cutter or a sharpened file and ‘turn’ your 4" circle.
While it is still spinning, GENTLY heat the disc with the heat gun, don’t hold it in one area, slowly heat the lot. It has to be just right (about 160C), get your polished dowel and from the centre gently drag it across the disc and start bending (cupping) it - don’t try and do it in one go, do it in about 3-4 passes, you only need about 3/8" -1/2" ‘dish’. Drill 3 x 3/8" equidistant holes around the 1.5" radius.
While you have the heat gun out, get the stem, and on one end spin it with your fingers in front of the heat gun to soften the end- when it gets soft, stick a swivel in the end and roll it between your fingers until cool. Cut a small ‘washer’ off the other end of the stem (1mm thick), put the sprinkler head through the disc and screw on the little washer you cut (this keeps these pieces together, so you don’t lose them)- screw on the stem - attach swivel to about 1' of bungy cord, and attach other swivel to the other end, put a split ring on and fit to the dog clip and you ar ready to ride.
Adjust the cord length, so the disc is just skimming the water, if there is no chop, don’t bother, unless you want to stand and rock the boat!!