There is a house in Ka'u with a rushing river that flows through the garage.

Well, that probably describes many houses in Ka'u. In Hilo and Volcano as well. Probably Wainiha and Kahalu'u, too.

On a rainy day, the water washes downhill in a grand sweep, turning the Ka'u carport into a boathouse.

The cats take up safe perches on the top of the washing machine to watch wide-eyed.

Mama moves the rubber slippers to the top step of the porch so nothing gets washed away.

The kids make boats and floats, rafts and surfboards out of anything they can find: trash-can lid, kamaboko board, empty bleach bottle, the broken lid of a long-discarded cooler.

If it's a just a little cloudburst, Barbie can go surfing on the kamaboko board. If it's a big rain, Kaipo and his friends can shoot the driveway surf on pieces of plywood.

Hawai'i is known around the world for fun in the sun. It's fun when it rains, too, but that's a big secret. There are those who know, but rarely talk about, the gleeful abandon of a rain-soaked day.

The tourists may be grumpily drinking their umbrella drinks under umbrellas, but all around the Islands there are underground cliques of daring adventurers who know how to have a good time on a rainy day.

Not that they're all particularly safe, mind you, but their creativity matches their recklessness.

Opportunities abound. Usually dry flood-control channels are flowing. Backyards become wading pools. Rain gutters shoot like fire hoses.

In places like Kalihiwai on Kaua'i, where the mountain stream empties into the ocean, a wild wave forms where the two bodies of water collide. Surfing that wave that never crashes is like one of those nouveau Olympic sports. On a dry summer day, the connecting point between the river and the sea is barely discernable.

Parks and school yards in various communities famously flood, attracting a host of youthful athletes somehow able to surf on 3 inches of water on a plank of soggy pressboard.

But it's not all harmless fun.

Sadly, last week, some rainy-day sportsmen went too far and a life was lost. Shooting the rain-produced rapids at usually un-rapid Nu'uanu Stream in kayaks might have seemed a good idea the day after flash flood warnings, but adventure outweighed prudence. Rainy-day frolicking comes with risks and limits. A healthy dose of caution is required.

If there are flash-flood warnings, stay away from streams. Don't surf in a parking lot full of broken glass and rusty metal. Electrical wiring and puddle jumping don't mix. Sometimes, scoop net fishing for medaka in the backyard or playing jabon race off the bridge is about as wild as you should get.

And sometimes staying indoors with a good book and a nice cup of cocoa is pretty fun, too.

Lee Cataluna's column runs Tuesdays, Fridays and Sundays. Reach her at 535-8172 or lcataluna@honoluluadvertiser.com.