A novel is a book bit it isn't paragraphs and lots of pictures
You should map out what you are going to write about in your body paragraphs (pre-writing, outline, four-square). What are the main points in each paragraph that could help you to form the statement? Once you have that, it should make writing the thesis statement a bit easier. If this is just a general overview, you could write something like, "Tchaikovsky's composition was shaped by many events that occurred early in life, during his adult life, and long after he passed away." Again, it would largely depend on what you want your reader to know about the paragraphs they are about to read.
You can write facts about the ocean and how us humans are damaging to sea corals with all of our pollution and the way it is affecting the sea or you can write about how there is an invasive animal in the sea which is the lion and how it is causing problems in the ecosystem in the ocean and how it is causing problems in other fishes daily energy consumed from other fish
