What can be done to discourage leeches from our beach area?
Unfortunately, not much. Getting rid of vegetation, rocks, and rotting logs, where leeches hide, would make your shoreline less hospitable, but—and this shouldn’t come as a shock—destroying your lake’s aquatic habitat is not a good idea. Not only is that sort of behaviour frowned upon (by basically everyone: your cottage neighbours, the other creatures in the water, the staff here at Cottage Life), it could be illegal. Also, it might not make a difference. Leeches are attracted to movement and vibration. The fact that you’re in the lake, swimming, is what keeps them coming back.
Make sure you aren’t unintentionally boosting leech numbers by causing excessive plant growth or nutrient loading by, for example, using soap, shampoo, or fertilizer in or near the lake. And don’t dump anything (fish guts, garbage, etc.) into the water that could translate into either food for the leeches or an extra hiding spot. It is legal to trap leeches if you have a valid sport-fishing licence. Submerge a metal can with a resealable lid, drilled with leech-sized holes and baited with raw meat, in the problem area. The leeches will swarm in through the holes, feed, become engorged, and then—suckers!—won’t be able to fit through the holes to get out.
Don’t leave the can in there too long (overnight is fine), though, since they can eventually wriggle back out, and when you remove it from the water, keep the lid on. Leeches can travel overland and might crawl up the sides and escape from the top.