MY GRANDMOTHER had a critical term for the pursuits of fun many of us fill our summers with.

With an intended zing, she called them "pleasure exertions" and noted that many come with their own unique troubles and travails.

For campers, the acid test is coping with mosquitoes or poison ivy.

For those who travel the interstates and back roads to see the "real America," there's white-line fever and car troubles.

For those who head to the water, there's sunburn and sharing the waters with that most unwelcome of organisms, the jellyfish.

The jellyfish, I'm sorry to note, arrived early and in large numbers this year in nearby waters.

In the Northern Neck and Middle Peninsula and in much of the Chesapeake Bay area, locals don't call them jellyfish or jellies.

Instead, when they spot the translucent stinging machines with mushroom heads and long, trailing tentacles, they call them nettles or stinging nettles, with a caustic curse tossed in for good measure.

In good years, when there's been plenty of spring rain and temperatures are fairly normal, the nettles don't arrive until after the Fourth of July.

This year they've come in early, and so heavy in spots that you can see dozens from any perch on a pier, though they can move in and out on the tides.

While these nettles are a real nuisance and will cause many to simply avoid getting into the water, the irritating critters are a way to tell real river folk from newcomers and novices.

Overwrought newcomers who haven't learned the ropes in places like Colonial Beach or Coles Point will see one nettle from the beach in the morning and immediately declare the river closed to swimming for their whole brood.

Natives and longtime residents will simply be a bit cautious when they wade in, picking up a nettle or two by their non-stinging heads and tossing them onto a nearby beach to put them out of business.

In a very real way, the presence of nettles in rivers like the Potomac and Rappahannock and the many creeks and smaller rivers that splinter off from them provides a test of mettle.