"We take 'em wherever we find 'em," Marlins vice president of scouting Stan Meek said. "He's just a guy who kind of jumped out at us. We're just happy to have him on our side."
• Marlins hope they got steal in Round 2 lefty
In the second round, Miami took Arizona State left-hander Brett Lilek with the 50th overall pick.
The Draft continues on Tuesday with Rounds 3-10. The MLB.com preview show begins at 12:30 p.m. ET, with exclusive coverage of Rounds 3-10 beginning at 1 p.m. ET.
Miami hasn't drafted a real power threat since Giancarlo Stanton was taken in the second round in 2007.
Naylor's body type, bat speed and power draw comparisons to Rangers slugger Prince Fielder.
"You hate to put a player on a guy, but there is some Prince Fielder in this guy. There really is," Meek said. "He's got that kind of bat speed. He's got that kind of raw power, which is really unique.
"I've talked to several scouts along the way who say, 'Wow, that body. We weren't sure about Fielder.' Again, this guy has got good tools, and we've seen them play against professional competition. [Fielder] would be the comp we'd put on him."
Naylor, who attended St. Joan of Arc High School in Ontario, turns 18 on June 22. The left-handed slugger calls it an honor to be mentioned in the same breath as Fielder.
"It's a good comparison," Naylor said. "Prince Fielder went pretty high in his Draft. He's made an impact in MLB since he's been there. Being compared to him is amazing."
On his club teams, Naylor traveled the United States to play against Division 1 and 2 college programs in the fall of 2013 and '14. In those games, he combined to hit .449 (83-for-185) in 56 games, with 23 doubles, 15 home runs, 62 RBIs, a .518 on-base percentage and a .838 slugging percentage.
A Red Sox fan, Naylor lists David Ortiz as his favorite player. But it didn't take him long to embrace his new organization. Naylor took to Twitter to say: "So honoured and proud to be selected 12th overall to the Miami Marlins."
"I looked at Papi because he is a game-changing player," Naylor said. "He can change the game with one swing of the bat. He's the leader on that team, and he always wants to win."
A member of the Canadian Junior National Team, Naylor has traveled the country and world the past few years. At age 15, he even participated in a Home Run contest at Marlins Park, winning the competition with a blast measured at 457 feet.
"He's had power for a long time," Meek said. "It's kind of incredible."
Since 2008, the Marlins have selected position players in the first round four times. All four have been left-handed hitters -- Kyle Skipworth (2008), Christian Yelich (2010), Colin Moran (2013) and Naylor.
Naylor has shown power hitting with wood bats. Meek said the organization has seen the first baseman hit with a wood bat on numerous occasions.
The Marlins also have seen him play against Double-A and Triple-A competition, and even face the Blue Jays, including knuckleball pitcher R.A. Dickey, a former Cy Young Award winner.
"This year we saw him actually play against the Toronto big club, and actually get a base hit off R.A. Dickey," Meek said. "I guess we figured if he can hit a knuckleball, then he can hit anything."
The 12th overall pick has a bonus slot value of $3,051,800, but that doesn't mean the team must sign the player for that exact amount.
Although he profiles mostly as a first baseman, Naylor may be able to play some left field.
But it's his bat and potential to impact a game with one swing that made him Miami's first-round choice.
"His kind of power really is unaffected by the size of [Marlins Park]," Meek said. "He will hit homers into the upper deck at this park."