Marine science includes all forms of general oceanography, physical oceanography (tides, waves, etc.), chemical oceanography (sea salts, properties of water, etc.), geological oceanography (mid ocean ridges, sea floors, hydrothermal vents, and other geologic things), and engineering (underwater technology.) Also, biological oceanography is kinda like ocean ecology, in the sense that marine biology is studying more individual organisms, and biological oceanography studies the whole ecosystem and it's interconnections.
Marine biology is the study of ocean life.
I hope that helped, at least some. I'm a firm believer that they're all very connected and one can not be understood without the others. (With the possible exclusion of engineering
... sorry all you engineers... no offense meant.)