Zelda: TOTK Whirly Swirly Things Quest Guide. The “big swirly thing” in the water Kula mentions is actually whirlpools that you can sometimes see in various large bodies of water in Hyrule.

Whirly Swirly Things Quest Reward Show the picture of the Sinkhole to Kula to complete the Whirly Swirly Things quest in Zelda: TotK. She will give you 5x Endura Carrots as a reward.