The Samoans, the 17th of the 20 teams to play, posted the first of their six tries after just 49 seconds, and were at point-a-minute pace through the first quarter at sunny Rotorua International Stadium.
Just four days after Namibia gave up four tries to Fiji winger Vereniki Goneva, Samoa star Alesana Tuilagi scored three and had another rubbed out. Kahn Fotuali'i and Paul Williams, after time in the sin-bin, added tries while the pack was rewarded for a relentless effort with a penalty try against a six-man Namibia scrum.
"We've been watching a lot of rugby the past couple of days, the boys were pretty edgy to get out there," Samoa captain Mahonri Schwalger said. "I was pretty happy with the way the boys played today. We've still got a lot of rugby to improve, so we're looking forward to Wales."
But Samoa has only four days before its hyped Pool D clash with Wales in Hamilton, and from the same side which shocked Australia in July it's likely to be without flyhalf Tusi Pisi (hamstring) and flanker Taiasina Tuifua (ribs). Both were playing leading roles before they left after 30 minutes.
Namibia was backing up just four days after losing to Fiji 49-25. It feared its largely amateur players would struggle to give two top performances in four days against two of rugby's most bruising national teams, but the tournament's lowest-ranked side gave another good account against the odds to notch second-half tries to backs Danie Van Wyk and Theuns Kotze.
"We were not going to out-skill a team like Samoa, we were not going to outpace them, but we can outwork them," Namibia captain Jacques Burger said. "We made a lot of mistakes, but we showed a lot of heart at the end. You can see the guys wanted to come back and they fought hard, and I'm very proud of my team."
Namibia's fightback had to begin from the first minute, when an attempted clearance kick into the wind hung in and was caught on the run in front of the grandstand by Fotuali'i. The scrumhalf shrugged off a high tackle and bowled through a low one to scamper 30 metres to the line. Pisi's conversion from the touchline and a penalty in the 10th made it 10-0.
Namibia then enjoyed being on top, but conceded ruck ball in front of the Samoa posts and lost a lineout throw in its own half, which ended with Tuilagi receiving an overlap pass from Tuifua to cross untouched in the 18th.
Another Pisi conversion and penalty, and it was 20-0 in as many minutes.
Pisi then blew a certain try when he was 10 steps from the right corner flag. Instead of carrying on, he cut inside and hurt his left hamstring when he was swallowed up. Tuifua also went off, gingerly holding his ribs.
The injuries slowed things down, a little. From a free kick, snappy handling by No. 8 George Stowers and replacement flyhalf Tasesa Lavea put the ball in the hands of Tuilagi, who crashed through three defenders in the left corner for his second try.
Just before the break, Williams was yellow-carded for a shoulder tackle on Kotze which dropped the Namibia flyhalf like a stone and caused a brief all-in melee.
Samoa was dominating territory and the set-pieces, and the only question at halftime was how it would fare playing into the wind. It fared fine.
Williams came out of the sin-bin just in time to land a penalty and Tuilagi bagged his third try, launched from another poor Namibia clearance kick.
A breakout by flanker Maurie Faasavalu saw Williams jink over near the posts, and he converted his own try for 42-0.
Namibia replied in style. A catch off his own chip by left winger Llewellyn Winkler set up Van Wyk, then Namibia's second try saw Kotze stretch out between the posts.
But in between, Namibia flanker Rohan Kitshoff was yellow-carded, and his short-handed scrum gave up the penalty try to Samoa.
When Namibia next plays big neighbour South Africa in Auckland on Sept. 22, it will be trying to avoid a World Cup-record 14th straight loss.
"Sometimes you play like amateurs when you don't play more of this kind of rugby, and we need to play more of this kind of rugby to be competitive," Namibia coach Johan Diergaardt said.
"Unfortunately, we are not rich enough to do this. But it is a part of us that we don't lie down and we didn't do that, so I'm pleased."
Samoa 49 (Alesana Tuilagi 3, Kahn Fotuali'i, Paul Williams tries, penalty try; Tusi Pisi 2 conversions, 2 penalties, Williams 3 conversions, penalty) Namibia 12 (Danie Van Wyk, Theuns Kotze tries; Kotze conversion). HT: 25-0.