der Taucher
diver
A person who stays and moves underwater, usually with special equipment such as breathing apparatus.
Der Taucher entdeckte ein altes Schiffswrack auf dem Meeresgrund.
The diver discovered an old shipwreck on the seabed.

diver
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diver
A person who stays and moves underwater, usually with special equipment such as breathing apparatus.
Der Taucher entdeckte ein altes Schiffswrack auf dem Meeresgrund.
The diver discovered an old shipwreck on the seabed.

The word 'Taucher' (diver) is derived directly from the verb 'tauchen' (to dive). The ending '-er' refers to the person or living being that performs the action — that is, someone or something that dives.
Er lernte im Urlaub zu tauchen.
He learned to dive on vacation.
When a person is meant, 'Taucher' (diver) is often combined with verbs like 'erkunden' (to explore) or 'entdecken' (to discover) and adjectives like 'erfahren' (experienced) or 'professionell' (professional).
Ein erfahrener Taucher führte die Gruppe an.
An experienced diver led the group.
You can tell from context whether a human or a bird is meant. Words like 'Ausrüstung' (equipment), 'Schiffswrack' (shipwreck), or 'Meer' (sea) point to the person, while 'See' (lake), 'Federn' (feathers), or 'beobachten' (to observe) point to the bird.
Der Taucher zog seine Ausrüstung an.
The diver put on his equipment.
swimmer
'der Schwimmer' and 'der Taucher' both refer to people in the water, but they are not doing the same thing. A 'Schwimmer' moves through the water by swimming, often at the surface or in a swimming pool. A 'Taucher' goes below the surface of the water and often uses special equipment, for example a diving mask or breathing apparatus. The words can be confused because both have to do with water sports and movement in the water. If someone is swimming, you say 'Schwimmer'. If someone is underwater and stays or works there, 'Taucher' is the right fit.

Am Wochenende untersucht der Taucher ein altes Boot unter Wasser.
At the weekend, the diver examines an old boat underwater.
Der Schwimmer trainiert jeden Morgen im Hallenbad.
The swimmer trains every morning at the indoor pool.