Although Ireland's loughs are probably the place that springs to mind for most people when it comes to mayfly fishing in still waters, there are some lochs in Scotland with good hatches that offer some fantastic fishing especially-but not limited to- Caithness. Oddly though, mayfly time seems to be less of and event than it is in Ireland, maybe because it comes a bit later in the highlands. Admittedly the hatches usually are not quite so prolific as on the likes of Mask and Corrib but they last longer, sometimes even until early August! I've had some amazing days on Mentieth, Hillend and others with both numbers and quality of fish, often wild, sometimes well mended overwintered rainbows depending on the loch. I often think Scotland's tourism board is missing a trick when it comes to some of the fishing that's available, but that might not be the worst thing in some ways.
Top: Melvin Octopus
Middle: Grace Kelly
Point: Lough Arrow variant.
I've mentioned in other FPs that I love wets, and given the choice I'd probably prefer to pull a team through the waves to targeting rising fish with dries, probably. Of course in real life we don't usually get the choice, the fish and conditions dictate. Either way, the chance of a 4lb wild fish coming up to either still is something pretty special. And I love the flies, wet or dry there's just something about the patterns for lochstyle mayfly fishing. The early days or weeks of the mayfly let you get away with some pretty fancy suggestive patterns but as the hatch continues you'll often find the need to get a bit more imitative. In fact it's one of the best times to get to terms with the concept of wets as imitative patterns- maybe that's a topic for another day.
As well as the yellow gosling in the picture, I've added a couple of pictures of nice wet fly casts that feature a mix of suggestivity moving toward more imitative patterns. Either would be a good starting cast that could be tweaked depending on how the fish respond.
Top: Muddled May
Middle: Western May
Point: Fordes May