OCEANSIDE -- Advance planning wasn't required, but it made all the difference when amateur boat-builders hit the water at Oceanside Harbor on Sunday.

Several hundred spectators got a firsthand lesson in that concept when they lined the harbor's edges to cheer on participants in the city's annual Nail and Sail boat-building competition.

Part of the city's annual Harbor Days celebration, which took place over the weekend, the contest challenged novices to build boats in two hours using a limited supply of materials.

The real test came at noon, when 12 three-member teams dropped their two-man boats into the water in groups of three for races across the harbor and back. Onlookers cheered madly and Oceanside City Councilman Rocky Chavez provided snappy play-by-play dialogue as boats underwent the "sink or swim" challenge.

Boats that failed to stay afloat, flipped, took on water or suffered from uncoordinated paddling efforts did in several teams fairly quickly.

Other vessels not only proved their seaworthiness but were surprisingly fast. They included a bright blue and yellow one built by members of the El Camino Real Rotary Club.

The team flew through the water to snap up its second first-place trophy. Keith Brentlinger, who provided paddle power for the club's entry, said early preparation was the key to the team's win this year as well as in 2002.

"Our No. 1 strategy is always build a prototype before," Brentlinger said. "In doing so, you kind of get the bugs out."

Now in its 24th year, the Harbor Days celebration is hosted by the Oceanside Chamber of Commerce and the city. The Nail and Sail competition has been a popular part of the larger event throughout its history.

Sharon Harrison of Oceanside was among those who lined sidewalks and docks overlooking Sunday's race. Watching the Rotary boat go head-to-head with one built by representatives of John Wayne's Glass in the race's second heat, Harrison said she has missed only one of the boat-building challenges in a 12-year period.

This time around, she brought along a friend named Lars who was visiting from Denmark.

"He can tell when the boats are going to sink even before they go in the water," Harrison said after yet another of her friend's predictions proved accurate. "It's that Nordic thing, I guess."

A few feet away, Anne West and Andy Taubman of Del Mar were watching their first Nail and Sail competition after reading about the event. The two knew none of the participants, West said, so they rooted for boats that looked well-designed.

The couple also took lots of mental notes after picking up information about entry requirements, with an eye toward possible participation in the race in the future.

"I've done things like this in the past," Taubman said. "There's always next year."

The final heat of the race pitted three teams of high school students against each other. Although none of their craft made it back to the launch dock, the teens elicited some of the loudest shouts of encouragement from the crowd, which seemed to like the idea of seeing them participate.

The high school category included a team from the School of Business and Technology, a charter high school in Oceanside where Chavez is its director.

He said he talked three of his students, all boys, into entering Sunday's competition. Calling themselves the SBT Slackers, the teens drew laughs from the crowd when their black box-like boat flipped over upon its entry into the water, then exclamations of amazement when the vessel remained afloat for a bit anyway.

Team member Kevin Wolf, 16, said the group ran out of caulk during the building part of the competition.

"We ended up using a mixture of sand and paint," he said. "And it floated!"

Contact staff writer Andrea Moss at (760) 739-6654 or amoss@nctimes.com.