Even though, by modern ideas, carracks were small (100 tonnes), they were still large by Tudor ideas. Sailors were used to sailing up rivers and carracks were too big for that.
So they built a slightly smaller version. It was called a caravel. It was about 50 tonnes.
It could go up rivers, but was only just good enough to cross oceans.
They had no 'castles' and needed carracks to protect them.