Lotte Baierl's interest in the underwater world first materialised on taking up the position as secretary to Hans Hass in 1943. However, Hans was unwilling to take Lotte on his research and filming expeditions, so, unbeknown to Hans, Lotte learnt to dive and take underwater photographs herself, in order to persuade Hans to take her on his expeditions. Borrowing Hans' camera whilst he was away lecturing, Lotte took images of fish in the Danube river which were published in an Austrian magazine, and soon Lotte became an established and accomplished underwater photographer in her own right.
In 1950, Lotte joined Hans' Red Sea expedition to shoot the Oscar winning feature film Under the Red Sea, and the two married on their return. One of the first underwater models, Lotte appeared in many of Hans' films and her appearances in only a swimsuit were said to be influential in the decisions as to when the films were screened and to their success.
Hans and Lotte co-produced and co-wrote many films and books documenting their adventures aboard their research vessel Xarifa, and in 1970 Lotte published Girl on the Ocean Floor, an account of her diving adventures with Hans.