BIG 'UNS: Rockfish season is open for a few more weeks in the lower Potomac and Virginia, and big cow rock have arrived there in numbers. "They're catching them steady," said Ken Lamb at the Tackle Box in Lexington Park, who reports that rock from 36 to 48 inches are abundant at the mouth of the Potomac, from the Coan River out to Smith Point and beyond.

Charter skippers are catching their two-person-per-day limits trolling umbrella rigs at various depths in deep water. This is not a good time or place for small boats, the Potomac being a treacherous body of water in winter. Among charter operators still running are Joe Scrivener, 301-994-0398; Eddie Davis, 301-872-5871; Jim Gray, 301-872-4022; Gregg and Steve Madjeski, 301-872-4215; Bruce Scheible, 301-872-5185; Butch Cornelius, 301-993-0347 and David Rowe, 804-529-6725.

RIVER CITY: The Potomac Conservancy holds its annual Celebration of the Potomac from 6 to 8:30 p.m. Thursday at Potomac Outdoors, 7687 MacArthur Boulevard, Cabin John. Tickets are $35, or $50 a couple. Call 202-338-4700.

OVERNIGHTER: Potomac Appalachian Trail Club has a Cabin Christmas foray scheduled next weekend in Syria, Va. Participants leave Friday evening and stay in a cabin heated by wood stove and share meals and hikes, plus cross-country skiing in the unlikely event of snow. Call John Koutze or Kathy McDermott, 703-846-9207.

CREEK WALK: Sierra Club has an eight-mile hike Saturday in Seneca Creek State Park, with some mild hill-climbs around Schaeffer Park. Leader is Dan Ryan, 301-622-5259.

IN THE MARSH: Blackwater National Wildlife Refuge near Cambridge is full of wintering waterfowl these days. Adding to the attraction today is a bookstore sale from 10 a.m. to 5 p.m. Discounts available on books, sweat shirts and nature-related items for youngsters. Also, guided tours, eagle walks and a puppet show are offered. Call 410-228-2677.

TRANSOM WIT: Every December Boating magazine awards prizes for the year's best boat names. This year's top awards went to "Eat, Drink and Remarry," a 21-foot Sea Ray in New Port Richey, Fla., and "Moby Debt," a 38-foot Carver in Richardson, Tex.