Durham — In the manual for “what you have to do right to beat Cromwell,” the Shoreline Conference girls' basketball tournament champion in five of the last six seasons, Old Lyme coach Don Bugbee would include the following:

“Everything.”

“Playing Cromwell, you have to be right on the money. You have to do everything correct,” Bugbee said Tuesday night. “They're really aggressive. They have the player of the year. They're good. They're 17-0 in our league and I don't think anybody came within 20 of them.”

Cromwell immediately foiled Old Lyme's hopes of perfection, however, hitting two 3-point field goals in the opening minutes — of the seven the Panthers would knock down in the game — to go up 8-0.

Top-seeded Cromwell finished with a 55-33 victory over No. 5 Old Lyme in the semifinals of the Shoreline tournament, advancing to meet No. 2 Coginchaug in Friday night's championship game.

“We played well tonight. That helps,” said Cromwell coach Kelly Maher, whose team is 19-3 and receiving votes in the latest GameTimeCT/New Haven Register state poll.

Shoreline Conference Player of the Year Jenna Serrantino had 18 points, including two 3s, and Vanessa Stolstajner 14 points. Stolstajner, also a Shoreline Conference first team pick, added two 3-pointers, as did Kelsea Corcoran, who hit the first 3 of the game from the left baseline.

Cromwell's players weren't exactly standing around waiting for the game to come to them.

Serrantino stole one floating Old Lyme pass and took it end-to-end for a layup in the second quarter to highlight a 14-0 run as the Panthers grabbed a 30-11 lead at halftime.

Old Lyme (15-7) began the second half with more of an aggressive stance, with Maddie Zrenda scoring four points in the first 34 seconds and Maher calling a quick, 30-second timeout, but Serrantino answered that with a pair of 3-pointers and Corcoran drilled a 3 at the buzzer as Cromwell took a 47-18 lead after three quarters.

Cromwell lost four starters from last year's team which won the Shoreline title, with Maher calling this season a learning process. She's seen the Panthers improve as the year has gone on, she said, with the seniors helping pull along the underclassmen, and Cromwell is also a proficient rebounding team despite not having a player bigger than 5-foot-10.

“It's something we've been working on,” Maher said of rebounding, which cost the Panthers in a 58-34 loss to top-ranked New London on Feb. 3. “It's our constant focus. We tell them it's about effort. … We knew Old Lyme was a strong fundamental team, so we had to be better than usual at everything tonight.”

Old Lyme, which will play next week in the Class S state tournament — while Cromwell moves on to Class M — got nine points from Zrenda and seven from Audrey Gavin. Old Lyme senior Jordan Lewis was named to the All-Shoreline second team and Zrenda was an honorable mention selection.

The Wildcats were coming off a 61-53 victory Saturday over No. 4 North Branford in the Shoreline quarters, getting 17 points from Gavin and 16 from Lewis. That avenged a 46-43 loss to North Branford earlier in the season.

“That was a hard-fought win over North Branford to even get here,” Bugbee said. “At their place, so that was an adventure. We played hard.”

Bugbee said this game against Cromwell was similar to the first time the teams met this season, when Old Lyme played better in the second half.

“Against them, everyone has to play the perfect game to the best of their ability,” Bugbee said. “Then maybe you have a shot.”

v.fulkerson@theday.com