Titanic vs Pennywise

The joke is a crossover between the horror movie 'It', where Pennywise the clown says 'They all float down here' and the Titanic. The Titanic responds like a person in a competition, meaning it's so good at making things float down that it would take on Pennywise's challenge and hold his beer. It's funny because of the juxtaposition of the two references and the idea that the Titanic is bragging about its sinking abilities.