[5] The landslide spawned a tsunami wave that struck multiple coastal regions in Banten and Lampung, including the tourist destination of Anyer.

[6] Lack of warnings on the arrival of the tsunami, coinciding with the Christmas and New Year holiday season in the nation, and night time setting in the area contributed to the large loss of life.

The newer system would detect any significant disturbances on water levels, including changes caused by volcanic activity or undersea landslide.

As such, in 1980, the Indonesian government set up a permanent volcano observatory in the island to observe its activity and to prevent another disastrous event in the region.

Researchers reported in 1995 that the subsequent eruptions of Anak Krakatau did not result in an infilling of the caldera and thus concluded that the possibility of a flank collapse could not be excluded.

In 2012, a study conducted by international researchers suggested the possibility of a major flank collapse on Anak Krakatau at some point in the future, which could produce dangerous tsunami waves.

However, owing to the population density in the region, insufficient mitigation measures could cause significant numbers of deaths and major damage to the area.

Starting in June 2018, Anak Krakatau saw an increase of volcanic activity with a Strombolian eruption, producing lava flows and ash plumes as high as 5 km.

One day prior to the collapse, on 21 December, an eruption was observed which lasted more than two minutes and produced an ash cloud 400 metres (1,300 ft) high.

[17] The Indonesian National Agency for Disaster Countermeasure (BNPB) spokesman Sutopo Purwo Nugroho said, "Dozens of buildings were destroyed by the wave, which hit beaches in Lampung and Banten about 21:30 local time (14:30 UTC) on Saturday.

"[10] According to The Jakarta Post, authorities said that the tsunami "may have been triggered by an abnormal tidal surge due to a full Moon and an underwater landslide following the eruption of Anak Krakatau.

[22] On 23 December, satellite data and helicopter footage confirmed that the southwest sector of the volcano had collapsed, which triggered the tsunami, and that the main volcanic conduit was erupting from underwater, producing Surtseyan-style activity.

[33] By 13:00 local time on 23 December, BNPB had confirmed 168 fatalities and 745 injuries with 30 having been reported as missing,[9] and the figure was further increased to 281 dead and 1,016 injured.

Eyewitnesses from the funfair recalled the tsunami struck with a height nearly as high as the light pole, with dozens, including children, reportedly dragged by the rushing wave.

[38] Indonesian officials stated that most of those who died were found inside villas and hotels, especially those located at Carita Beach, Banten.

After one day being announced missing, drummer Windu Andi Darmawan and Dylan Sahara, wife of Seventeen's vocalist Ifan were reported to have been found dead.

[57] The Indonesian government stated that the tsunami caused an estimated total damage of 150 billion rupiah in Tanjung Lesung alone, which is a popular tourist hotspot located in Pandeglang Regency.

[70] These lessons have collectively contributed to more robust and comprehensive disaster preparedness strategies worldwide, potentially saving lives in future events.

[75] President of Indonesia Joko Widodo ordered an immediate field response by BNPB, the Social Ministry, and the Indonesian National Armed Forces.

[81] Ministry of Internal Affairs stated that emergency funds would be provided to repair damaged government buildings in Banten and Lampung.

[83] The Coordinating Minister for Human Development and Culture Puan Maharani stated that the government would provide a 15 million rupiah compensation to each of the victims.

[86] On his second visit on 2 January, he ordered every local officials in Lampung and Banten to relocate, reconstruct and to "redesign" the coastal residential and commercial zone that are located on the coast.

[94] In South Lampung Regency, the Indonesian National Board for Disaster Management announced that they would build temporary housing for the survivors.

[100] Crescent Star Party set up a command center in Serang Regency, Banten for the management of the aids distribution.

[107] Ignasius Jonan, Minister of Energy and Mineral Resources, dispatched 17 Emergency Response Team from his ministry to the affected areas.

[114] Meanwhile, the Indonesian National Board for Disaster Management warned coastal residents that there was a possibility that another tsunami would strike the region again, citing the unstable condition of the slope due to the landslide.

[133] A public fundraising conducted by the Singapore Red Cross managed to collect a total of S$80,000, which would be used for buying aids and supplies for the survivors.

[138] New Zealand Prime Minister Jacinda Ardern extended her condolences and offered relief and recovery efforts to Indonesia following the tsunami.

[139] New Zealand Minister of Foreign Affairs Winston Peters stated that the government would send $1.5 million to help the recovery efforts through the International Federation of the Red Cross.

[140] Japanese Prime Minister Shinzo Abe immediately phoned President Joko Widodo to offer his condolences and also stated that Japan would provide aid to Indonesia.