Thud, thud, silence, and again, thud, thud.
These days only the sound of officers stamping passports breaks the quiet at the immigration queue at the Batam Centre International Ferry Terminal.
Ferry passengers from Singapore and Malaysia, one moment boisterous and chatty after disembarking, automatically zip their lips when they enter. To speak, even in a whisper, could lead to deportation - and ruined holiday plans.
Ferry operators and passengers told The Sunday Times that Batam immigration officers have recently begun enforcing silence strictly.
When The Sunday Times visited the Batam terminal last Thursday, signs pasted on pillars showed a picture of a raised finger over a pair of lips.
But that warning can escape some visitors, who end up perplexed when told suddenly to take the next ferry back to Singapore because they were caught speaking.
Mr Guo Kai Kai went to Batam late last month for a weekend getaway with four friends. The 25-year-old, who works in the maritime sector, was chatting in the queue when he and a friend were told to leave.
He said an immigration officer had earlier warned them to stop talking, but he had "no idea the penalty was going to be so harsh".
"I was there for a holiday - why couldn't I open my mouth? I was just chit-chatting with my friend," he said, adding that it was unreasonable to remain silent if the queue was long.
Mr Guo said he was waiting in line for half an hour.
The pair were led to the departure hall by an immigration officer, who told them to get on the next boat to Singapore, which they did.
"We were not even given the chance to explain and apologise," he said, describing how they had pleaded with boarding agents to let them speak to the authorities but were flatly refused.
The trip to Batam takes about an hour each way and a round trip costs about $50, including surcharges and terminal taxes.
Mr Guo and his friend did return to Batam. When they got to Singapore, they took another boat to Sekupang, a different ferry terminal on Batam, at an extra cost of about $50 each.
Ferry operators said the same rules apply at Sekupang too, but are not so strictly enforced.
Ms Nur Intan Syafinaz, who visited Batam a few weeks ago, told The Sunday Times that she saw families being split up because one member was forced to turn back after being caught talking.
"There was one woman who was pleading with the officer to let her in because her whole family went through except for her," said the 23-year-old flight attendant.
Some tourists sent back do not return, and cancel their bookings with Batam hotels.
"Sometimes they call to ask us to waive their fees but we can't help them all the time," said a manager at Harris Hotel Batam Centre, who declined to be named.
The three ferry operators with services to Batam Centre - Batamfast, WaveMaster Holidays Club and Sindoferry - said they send back between five and 15 people each every week, mostly over the weekend.
During peak holiday periods, as many as 50 may be sent back in a week, said Mr Shahzan Shah, Wavemaster's operational manager in Batam Centre.
"Batam Centre is quite strict. If you talk, laugh loudly or behave inappropriately, they will take action," he added.
Mr Danny Lim, a ticketing agent for Batamfast, said officers started clamping down on noisy tourists around the start of this year. He said hapless passengers often turned to the agents for help but there was nothing they could do.
Mr Shahzan said: "I wish we could help, but unfortunately we are not the government."
Many travellers have gone online to complain. Travel forums like Tripadvisor are filled with accounts by people who had to leave before their holidays began.
Tripadvisor user TangGuo, from Singapore, wrote that immigration officers were rude and unprofessional when they told his aunt and mother to turn back during a family trip in May.
He alleged that an officer beckoned his aunt to accompany him to a corner, saying: "You talk, you go back Singapore."
"My mum didn't hear what happened and asked him what was going on and he shouted, 'You also go back'," he added.
The situation has led some tour agencies to issue advisories to customers.
Ms Amanda Wang, from Sea Wheel Travel, said that after four of its customers were turned back last month, the firm started telling its travellers to stay quiet.
Another agent, Ms Hann Kamarudin from Batam Holidays Travel, said tourists should make sure they do not run afoul of other rules. For starters, travel documents should be in order, and visitors should not use cellphones while in the immigration queue.
The authorities in Batam defended their approach.
Batam Centre Immigration Office chief Irwanto Suhaili said his officers needed the quiet to maintain order.
Otherwise, tourists would not be able to "hear us when we call their names or ask them to step forward", he told The Sunday Times.
He said some visitors had only themselves to blame. They turn up drunk, talk loudly, use their phones and rush instead of queuing orderly, he said.
"If I come to Singapore, you would expect me to respect your rules. If you come here, you should also respect ours," he added. "If you follow the rules, there would be no problem."