Mwalola wa Mwalola, a longtime fisherman in the Indian Ocean on the Kenyan coast, vividly remembers the events of the deadly tsunami of 20 years ago.

Mwalola said the fisherfolk's experience and knowledge of the ocean saved his life after they sensed danger and decided to keep off the ocean on the fateful day.

“My place of work was hit, but I was not affected because I heeded the warning," he said. "We avoided losses because we warned our colleagues of the impending danger and asked everyone to keep off the ocean that day.”

On December 26, 2004, a powerful earthquake off the coast of the Indonesian island of Sumatra generated a devastating tsunami that was observed worldwide and caused tremendous devastation and deaths throughout the Indian Ocean region, including in East Africa.

Out of the 228,000 people killed, more than 300 were from the East African countries of Somalia, Tanzania and Kenya, according to the U.N. Educational, Scientific and Cultural Organization.

The disaster raised awareness about the threat tsunamis pose to coastal communities around the world and the need for improved tsunami detection, forecasting, warning and preparedness.

Observers say more remains to be done in the East African countries that were affected.

Shamim Wasii Nyanda, an environmental activist at the Tanzania Ocean Climate Innovation Hub in Dar es Salaam, said, "There’s an increase of vulnerability due to climate change but also ... limited adaptation funding. Most of the coastal cities lack sufficient financial resources to implement these climate adaptation measures, particularly in urban, under-resourced communities. They do not have that kind of technology or resources for them to be able to work on these problems that we are experiencing," especially tsunamis.

Nyanda said increasing urbanization is compounding the risk.

“Coastal cities like Dar es Salaam itself have continued to expand, with informal settlements encroaching on vulnerable areas where facilities like disasterproof housing and infrastructure are not available." People then build housing in areas where they shouldn't, "so, when these disasters come, like the tsunami, they are not prepared. They do not have the technology. They do not have the infrastructure … and what happens? They are just swept away.”

As countries observe the 20th anniversary of the 2004 tsunami, experts say preparedness, prevention and mitigation measures are key in preventing such disasters in the future.