“This weekend shellfish gatherers will rejoice, but ferry riders and pleasure boaters might cringe when the moon shows its massive force by creating the lowest and highest tides of the year. A few vehicles with low-ground clearance could have trouble boarding ferries, and a few trips will be cancelled on the Keystone-Port Townsend route on the mornings of July 1 to July 5, according to officials with Washington State Ferries.Boaters must also be careful to stay away from shallow water.Dave Williams, harbormaster for Oak Harbor Marina, said about three or four people run their boats aground every summer during low tides.“We have an especially tricky entrance on the north side of the marina,” Williams said. “It requires close adherence to the marked channels.” Williams encouraged boaters to stay within the markers, check charts and plan trips to avoid the most extreme tides. Otherwise, when boats get stuck they have to sit in grand display for all the marina to see, he said.On Friday, shellfish connoisseurs took advantage of the already low tides in Penn Cove.“The big ones are usually way down, but they were up near the surface today,” Paulette Smith said. If clammers thought it was good with Friday’s minus 2.7 tide, they can expect to be gorging themselves Sunday.Sunday’s low tide is expected to be minus 3.7 feet at 11:57 a.m., while Monday’s and Tuesday’s high tide is expected to be 12.8 feet at 8:10 p.m. and 8:55 p.m., respectively. Though Sunday’s low tide will be extremely low, it won’t be a record breaker. The really memorable ones show up every 19 years, and a minus 4.5-foot low tide is expected in 2007.Residents of Washington can purchase shellfish licenses for $8 that last until March 31, 2001, and non-residents can purchase a 2-day license for $7 or a year-long license for $20.The limit on clams is a combined total of 40 littleneck, butter, cockle, eastern softshell and macoma clams and the first 3 geoduck and first 7 horse clams found. Eighteen oysters are allowed, but they have to be at least 2.5 inches wide.”