der Schwimmer
swimmer
A person who swims, either as a sport or as a leisure activity.
Der Schwimmer erreichte als Erster das andere Ufer.
The swimmer was the first to reach the other shore.

swimmer
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swimmer
A person who swims, either as a sport or as a leisure activity.
Der Schwimmer erreichte als Erster das andere Ufer.
The swimmer was the first to reach the other shore.

The word 'der Schwimmer' (swimmer) is derived directly from the verb 'schwimmen' (to swim). The ending '-er' is often used in German to indicate a male person who performs the corresponding activity.
Er lernt gerade schwimmen.
He is just learning to swim.
The context tells you which meaning is intended. If you are talking about sports, it refers to a person. In technical contexts such as a toilet tank, it is a component. In fishing, it is the bite indicator on the water.
Der Schwimmer im Vergaser meines alten Autos klemmt manchmal.
The float in the carburetor of my old car sometimes gets stuck.
When referring to a person, 'Schwimmer' (swimmer) is often combined with adjectives that describe ability. Typical expressions are 'ein guter Schwimmer' (a good swimmer), 'ein geübter Schwimmer' (an experienced swimmer), or 'ein schlechter Schwimmer' (a poor swimmer).
Auch als guter Schwimmer sollte man die Strömung nicht unterschätzen.
Even as a good swimmer, you shouldn't underestimate the current.
pose
'der Schwimmer' and 'die Pose' can mean the same thing in fishing: a small object on a fishing line that floats on the water and indicates a bite. In this context, the words are synonyms. However, they are easy to confuse because both words also have other meanings. 'der Schwimmer' is usually a person who swims, or a technical part. 'die Pose' is usually a body posture or an affected way of behaving. Only in fishing does 'Pose' mean the same thing as 'Schwimmer'. So pay close attention to the context.

Zum Angeln braucht Paul einen kleinen Schwimmer für die Schnur.
Paul needs a small bobber for the line to go fishing.
Die Pose verschwand plötzlich unter Wasser, und Tom zog die Angel hoch.
The float suddenly disappeared underwater, and Tom pulled up the fishing rod.