Learn Spanish (Spain): Nosotros viajaríamos por el mar en nuestro nuevo yate.

For regular verbs in the conditional tense, you keep the entire infinitive and add the ending. Here, we add the nosotros ending -íamos directly to viajar, making viajaríamos. Notice that all conditional endings have an accent on the í.

Why do we use por instead of en in the phrase por el mar?

We use por to indicate movement through, across, or along a physical space. Because they are moving across the water, por el mar is the correct way to express this travel route in Spanish.

Why is nuevo placed before yate instead of after it?

Placing nuevo before the noun often means it is newly acquired by the speaker, rather than brand new from a factory. nuestro nuevo yate emphasizes that it is a new yacht to them, whereas nuestro yate nuevo would focus on the physical, freshly-built condition of the boat.

Could we drop the word nosotros from this sentence?

Yes, you can almost always drop subject pronouns in Spanish. The -íamos ending on viajaríamos already makes it perfectly clear that 'we' are the ones traveling. Including nosotros here just adds a little extra emphasis.