This is the 11525th most frequent Polish word.
kajakarza
"Kayaker" – a person who paddles a kayak.
Here, 'kajakarza' is used as a masculine singular accusative case of 'kajakarz', denoting the person who is kayaking and is the direct object of the verb.
Kajakarza widziano, jak płynie po rzece.
The kayaker was seen paddling down the river.
Here, 'kajakarzem' is the masculine singular instrumental case of 'kajakarz', used to indicate the instrumentality or accompaniment relating to the conversation.
Rozmawiałem z kajakarzem o trudach wyprawy.
I talked to the kayaker about the challenges of the expedition.
In this sentence, 'kajakarz' is in its nominative case, used as the subject, referring to the person standing on the shore.