Lewis, who hit the headlines last summer after becoming the first person to swim the entire length of the Thames, has completed more swims around famous landmarks than anyone in history and is the only person to have swum in all five oceans.
Lewis has a unique ability to withstand extreme cold by raising his core body temperature, and has completed all of his swims in just a swimming costume, cap and goggles. He has also had to contend with polar bears, great white sharks, hippopotamuses, leopard seals and crocodiles.
All of Lewis' swims have involved a link with science, and he sponsored a number of leading scientists to accompany him on his endurance feats in order to enable them to study the impact of cold on human performance.
The address, which will take place from 1.45pm to 3.30pm in Lecture Theatre 3 of the School of Chemistry, Cantock's Close, is part of Bristol City Council's Primary Gifted and Talented Initiative.