Seal commonly refers to:

• Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals
• Seal (emblem), an emblem used as a means of authentication; both an impression in paper, wax, clay or other medium, and the device used
• Seal (mechanical), a device which helps prevent leakage, contain pressure, or exclude contamination where two systems join
• variant of English for decal or sticker

The United States Navy's Sea, Air and Land Teams, commonly known as the Navy SEALs, are the U.S. Navy's principal special operations force and a part of the Naval Special Warfare Command and United States Special Operations Command. One of the SEALs' primary functions is to conduct small-unit maritime military operations which originate from, and return to a river, ocean, swamp, delta, or coastline. SEALs can negotiate shallow water areas such as the Persian Gulf coastline, where large ships and submarines are limited due to depth. The Navy SEALs are trained to operate in all environments (Sea, Air, and Land) for which they are named. SEALs are also prepared to operate in a variety of climates, such as desert, arctic, and jungle.