He could have kept going, looked the other way. But on Tuesday afternoon, when Peter Stankiewicz saw that the cab of a tractor-trailer had plunged into the Potomac River from the Cabin John Bridge, he stopped his Datsun and dived into the 35-degree water. Someone had to save the driver, he figured.

A few minutes later, he had freed the semiconscious driver, dragged him through the rainswollen river to the bank, and administered mouth-to-mouth resuscitation. And though he was too late and the driver eventually died, Stankiewicz became an All-American Hero, King for a Day in samaritan annals.

It ended up costing him $25. His car was towed away.

When the professional rescue workers arrived and loaded Stankiewicz into an ambulance to take him to Suburban Hospital for treatment for exposure, Stankiewicz says, he "asked the policeman if he could move it [his car] for me. He said, 'Don't worry, we'll take care of it.'"

They took care of it. They called Poor Richard's Crane Service in Rockville. At first, Poor Richard wanted to charge poor Stankiewicz $45. But, said a Poor Richard employe, "We figured it was kind of ridiculous for someone to go jumping off a bridge to help somebody and then get charged for it . . . we knocked off the $20 impoundment fee."

A Maryland state police spokesman said yesterday that the car was towed "due to the traffic tie-up" and to "protect his vehicle."

Wasn't there some way you could have arranged for Mr. Stankikewicz's fees to be waived? the spokesman was asked.

"We're working on it," came the reply.

Stankiewicz is taking it in stride, enjoying more than his share of his 15 minutes in the spotlight. "The guys at work bought me a plunger to flush out crime and a Superman T-shirt, but they're really burned about this.

"I guess there's a moral here."