To boil the ocean, in a business context, is to increase the scope of a project or task until it is practically impossible to accomplish as envisioned.
Project management employs a number of mechanisms to keep the scope of projects within reason. The most essential practice is ensuring that requirements are clearly documented in the project plan and are understood by all parties. Accordingly, further requests can only be addressed through change requests. The common tendency for project requirements or scope to steadily increase is sometimes known as feature creep or scope creep.
The term "boil the ocean" is usually attributed to Will Rogers, an American humorist. Rogers is said to have suggested boiling the ocean as a way to deal with German U-boats during World War I: "You just boil the oceans. The U-boats will turn pink and pop to the surface. Then, you just pick them off." Shrugging off the question of how to actually boil the ocean, Rogers just said that he never worries about details.