Tsunami slams into concert venue in Indonesia; dozens reported dead.

This happened resulting from the Volcano Anak Krakatoa erupting and an ensuing Tsunami that hit the mainland 24 minutes later.
At least 168 dead so far in Indonesia.
https://www.cnn.com/2018/12/22/asia/deadly-tsunami-indonesia/index.html
The 305m-high (1,000ft) volcano is about 80km off the west coast of Java and has been erupting since June. In July, authorities widened its no-go areas to 2km from the crater.

Officials say it is rare for eruptions to trigger a tsunami which might explain the initial confusion in not calling it a tsunami.
There is a bit more detail about where the fatalities have occurred.

The worst affected area was the Pandeglang region of Banten province in Java, which encompasses the Ujung Kulon national park and popular beaches, the disaster management agency said. Of the deaths, 33 were in Pandeglang. There were at least three people dead in Serang, which is further north.

Alif, a resident in Pandeglang district who goes by one name, was quoted on Associated Press as saying that the tsunami reached about 3 metres (9.84 feet) high. He told MetroTV station that many people were still searching for missing relatives.

The waves also spread west to Sumatra. In the city of Bandar Lampung on southern Sumatra, hundreds of residents took refuge at the governor’s office.