BATH — Third-seeded Oceanside withstood a late-game rally to hold off second-ranked Morse for a 10-9 victory Friday in a Class B North girls’ lacrosse semifinal at McMann Field.

The Mariners (12-2), who defeated the Shipbuilders for the first time in the program’s four-year history, will be in the regional final Wednesday against St. Dominic or Yarmouth, who meet Saturday.

Morse (11-3) beat Oceanside twice earlier this season.

On April 28, the Shipbuilders coasted to an 8-4 win over the Mariners at Pendleton Field in Thomaston. Last Saturday, Morse ran away with an 8-1 win over Oceanside in the Kennebec Valley Athletic Conference Class B title game.

“We came into the game real nervous because we had already lost to them twice, but we were ready to put up a fight,” said Jillian Brooks, who led the Mariners with four goals.

“The key was that we played well as a team today, and our midfield passing was good,” Oceanside Coach Angela Vachon said. “We’ve been working in practice on sharper passes. To Morse’s credit, we tried to emulate them because they are an exceptionally good team.”

The Mariners (12-2) led 6-4 at halftime, then gradually pulled away.

Oceanside opened a seemingly comfortable 10-6 lead when Brooks wove her way through the defense to score her fourth goal with just over 10 minutes remaining.

The score remained 10-6 until Morse scored three goals late in the game.

“They just played Freeport and they won in overtime,” Vachon said. “I knew they could make that happen.”

In the quarterfinals, Morse pulled out a 10-9 victory against the seventh-seeded Falcons in overtime.

Amanda Gagne began the late-game rally by scoring two goals 24 seconds apart to make it 10-8 with 43 seconds left. With 18 seconds remaining, Emily Martin scored her third goal to bring the Shipbuilders within 10-9.

Morse won the midfield draw for the third straight time, but Oceanside goalie Elise Laslavic stopped a shot from inside a number of players in front of the crease to preserve the win.

“We’ve studied (Morse) for a long time,” Vachon said. “We’ve been watching and trying to run our practices so we could get to this point.”

Gabby Straka had two goals and an assist for Oceanside. Sydney Hall scored two goals, and Julia Barbour and Nicole Ladd each scored once. Sierra Beal had two assists and Emily Tyler added one.

Noa Sreden had two goals and an assist for Morse.

“(Oceanside) maintained possession,” said Jessica Avery, the co-head coach of the Shipbuilders. “We had kids today who normally never drop the ball who dropped the ball and Oceanside capitalized on it by keeping possession, and that’s how you win the game.”

“We know them and they know us,” said the other co-head coach, Linda Levesque. “(Oceanside) played the way we usually play. We just didn’t play well today.”