Corona del Mar High head coach Barry O'Dea pumps up the crowd as the Sea Kings lead 7-6 with seconds remaining on the clock during the fourth quarter against Newport Harbor in a CIF Southern Section Division 1 quarterfinal match on Saturday. (KEVIN CHANG, Daily Pilot / November 10, 2012)

CORONA DEL MAR — Before what could have possibly been the last match of the season, the Corona del Mar High boys' water polo team and coaching staff met.

The Sea Kings are a senior-heavy team, with 13 of them. They talked about their fears, and a big one was that Saturday night's CIF Southern Section Division 1 playoff quarterfinal could be their last game in their home pool.

"They all agreed, 'We're afraid it's going to come to an end,'" CdM Coach Barry O'Dea said. "We talked more about it, and we addressed it. We reminded them in the second half tonight that we've got to overcome this fear. We've got to go after these guys, go after this win. Don't let that happen. The way that you beat a fear is you conquer it."

CdM fell behind Back Bay rival Newport Harbor by three goals early in the second half. Seconds before that, a key starter had fouled out.

But No. 4-seeded Newport Harbor would not score again.

The Sea Kings not only conquered their fears, they ended their rivals' season.

Armen Mavusi scored the game-winning goal with 4:05 left on a redirect from Colby Watson as the Sea Kings rallied to stun the Sailors, 7-6, and advance to the Division 1 semifinals.

Reid Chase made a steal with 14 seconds left to help preserve the victory, sending CdM (23-6) into the semifinals on Wednesday night. CdM will play top-seeded Mater Dei, the two-time defending champion that beat Harvard-Westlake, 15-6, in another quarterfinal, at 7 p.m. Wednesday at Irvine's Woollett Aquatics Center.

Do not count CdM out. The Sea Kings showed Saturday night that they indeed had no fear.

Their chances looked slim in the third Battle of the Bay meeting of the season. They were down, 5-3, at halftime, after Newport Harbor senior Curtis Fink scored on an outside shot at the buzzer. They fell further behind in the third quarter, after senior lefty Jake Wyatt fouled out.

Newport Harbor (21-7) converted the six-on-five, with senior co-captain Preston Lee finding Mitch Mendoza on the right side with 5:11 left in the quarter.

The Sailors would not score again in the final 12-plus minutes. Watson, CdM's emotional leader in the water, had a big second half.

"We've been a family for four years," said Watson, one of four team captains along with Chase, Kyle Trush and Patrick McKenzie. "One of our family members had to go out, so we just had to cover for him ... [Beating the Sailors] is sweeter than pie. I have a different choice of words, but it can't be published. We were excited to play them. We weren't scared. We knew that if we shut down Dan [Stevens] and Curtis, they wouldn't have anyone to go to."

Chase, who scored all three of the Sea Kings' first half goals, started the comeback with a goal from the left from a tight angle. Then, after earning an exclusion, Chase fed center Ty Hack for a quick goal that trimmed CdM's deficit to 6-5.

"Reid Chase was the best player in the pool tonight," said O'Dea, who beat Newport Harbor for the first time in four postseason meetings. "He just took the team on his shoulders and said, 'I'm not going to let this team lose.'"

After CdM killed off a Newport Harbor six-on-five early in the fourth quarter with a Watson field block, he tied the score at 6-6 with 5:34 to go. After the goal he pointed into the stands to his older brother, Chase Watson, the 2010 Newport-Mesa Player of the Year who now plays at USC.

The Sea Kings later got a chance to go up, but Newport Harbor senior goalie Wyatt Muller (six saves) came up with a big penalty-shot block on Chase. The penalty shot occurred after Newport Harbor senior Blake Grove fouled out for making a play on the ball after he was already called for an exclusion.

Chase said he didn't dwell on the missed opportunity. The Sea Kings instead surged into the lead for the first time all night on Mavusi's counterattack goal, which came after a perfect pass from Watson.

"I was having a rough game, and I wanted to make up for it," Mavusi said. "I just swam as hard as I could."

Newport Harbor had two more six-on-five chances, but couldn't find the mark. The Sailors finished the game two of eight on the power play; CdM was three for seven.

To Newport Harbor Coach Robert Lynn, the second-half collapse was nothing new.

"We've been trying to change that the whole year," Lynn said. "We have a good first half, and then ... the guys felt tight under pressure again. It seems like we were thinking about using the time, instead of attacking."

The Sailors got another great chance to even the score with a minute to go. Stevens, a senior co-captain who was praised by CdM's players for playing through a ruptured left eardrum, stole the ball and found Fink on the counter.

But CdM's Trush stayed in position behind Fink, with his arms up, and teammate Danny Marshall got there to steal the ball.

Newport Harbor got one last chance with 32 seconds left, calling timeout after Lee stole the ball near mid-pool. But a pass from Ryan Warde inside to Stevens was picked off by Chase, and CdM was able to run the clock out after that.

"I fouled Warde," Chase said. "I knew he was going throw it in, so I just hustled back and stole the ball. Jack [Harryman] did a great job containing."

Chase scored a game-high four goals for the Sea Kings, also including a quick lob shot from the left. Harryman (two steals), Marshall, Trush and Watson all had field blocks, and McKenzie made four saves. Chase and junior Matt Sherburne each drew two exclusions.

"Honestly, what got us back in the second half was our two-meter men," Watson said. "They never stopped working. Sherburne had an awesome game. He played out of his mind and stepped up big. He's a junior, and he played like he's been here many times before. Armen and Ty, they were having rough games, but just the fact that they never stopped swimming and never stopped trying was huge for us."

Fink had three goals and drew three exclusions for the Sailors. Warde also had a goal and two field blocks, and Stevens finished with three steals. Grove played set defense most of the night for the Sailors, and he had a pair of steals.

CdM now has a couple of days to try to figure out Mater Dei. Coach Chris Segesman's Monarchs will come into Wednesday night's semifinal on a 77-match winning streak, a Southern Section record.

"It's a great matchup," O'Dea said. "They're really good, and we have nothing to lose. Obviously, we've got to be creative and find a way to beat this team. They're pretty dang tough. As Chris says, 'Pick your poison,' so we're going to find which poison hopefully works best for us. It should be exciting."

matthew.szabo@latimes.com

Twitter: @mjszabo