In the USA they use a planer to take the lure down to a certain depth, a No 2 planer will hold your lure about 10ft under the surface at 2 / 3 knots, the bigger the No the deeper the planer will dive.
When a fish hits the lure , pressure is taken of the planer & it comes to the surface so you are not fighting the planer as well as the fish.
They are pretty cheap, made of stainless steel & cost about $7 .
The trace length from the planer to the lure wants to be about 20ft or more, too short & some fish will hit the planer , which then will come to the surface & will need to be reseat.
You should be able to buy these direct from any USA fishing outlet on line, or if you know somebody going over get them to bring back a few.:boat: