What did Cortes do so his men could not retreat or go back to Spain?

According to HIstory.com

Faced with an Aztec revolt against their rule, forces under the Spanish conquistador Hernan Cortes fight their way out of Tenochtitlan at heavy cost. Known to the Spanish as La Noche Triste, or “the Night of Sadness,” many soldiers drowned in Lake Texcoco when the vessel carrying them and Aztec treasures hoarded by CortÝs sank. Montezuma II, the Aztec emperor who had become merely a subject of Cortes in the previous year, was also killed during the struggle; by the Aztecs or the Spanish, it is not known

the first part is ocean

explanation:

it apply by theyre artifacts