I can't help you directly, but more detail will likely help others respond. What model motor? What kind of quantity is "a lot" and what is "not so much". Can you correlate any facet of engine operation (e.g., heavy loading, lots of transmission shifting) with the quantity of water you find?
Is the "water" fresh water, salt water, or coolant? Is it mostly water, or mostly hydrocarbons?
Have you visually checked for active leaks, or signs of a leak that can be traced back to a point of origin? Verifying whether it's oil vs. diesel will help a lot. Are ALL your hose clamps tight? Are ALL the hoses in good shape? Oil drain plug tight? Is the raw water intake leaking at the thru hull?
If you are not single handing, you may want to observe the engine while underway. If you do so, be extremely careful to avoid moving/rotating parts with your clothing, hair, and other body parts. Good luck.