Swimmer (noun)

1. A person who swims, either as a sport or as a means of transport or recreation.
2. A device or machine used for swimming or propelling oneself through water.

Origin:

From middle english swimmer, from old english swimman "to swim".

Examples:

1. The swimmer dove into the pool.
2. The swimmer won a gold medal at the Olympics.
3. She is a strong swimmer.
4. The river was full of swimmers enjoying the warm weather.
5. The swimmer robot was used to collect data in the ocean.