If "sub" refers to a submarine:
* Surface vessel: This is a general term for any ship that operates on the surface of the water, like a destroyer or a sailboat.
* Aircraft: Planes operate in the air, which is the opposite of underwater.
If "sub" refers to a substitute (like a substitute teacher):
* Regular: This refers to the usual, permanent person or thing, like the regular teacher.
* Main: Similar to "regular," this emphasizes the primary, non-substitute person or thing.
If "sub" refers to a subscription:
* Unsubscription: This is the act of canceling a subscription.
* Free: This implies not having to pay for a subscription.
If "sub" refers to a prefix meaning "under" or "below":
* Super: This prefix means "above" or "beyond."
* Over: This prefix also means "above" or "beyond."
Please provide more context about how you are using the word "sub" so I can give you a more specific and accurate opposite.