Use a bigger float and a bigger lead, fish overdepth with the lead touching the bottom. If the current is not too strong, the lead will drag and then hold.
But in some swims the current will be too strong, either:
1 - the float will sink under the force of the current, but the lead holds on the bottom.
or 2- both lead and float are dragged downstream. In this case add more lead or reel the float nearer to the bank, where the current should be less powerful.
If you are fishing with the lead dragging the bottom, it's sometimes better to rig the float so that it is attached bottom only (like a waggler) rather than sliding through the centre of the pike float. With a waggler style set up, bites are spootted earlier, since you normally get a gentle lift bite before the float sinks away.