Curiosity's theme is that curiosity is necessary for living – not life, but living. Those who have curiosity and don't conform to society are often looked down on by other members of society. This is exemplified in the last stanza.
The sea has waves. They go up and crash back down. You can think of this as hard times. When you think your doing good and start rising to the top you often crash back down. This (the crash) leads to difficulties or troubled times.
