If your oc is an mermaid in this: All your life you heard how bad humans are. But one day curiosity got the better of you leading you to almost getting seen by an human (Your oc's crush).

If your oc is an regular human in this: You were traveling in a boat (Or was swimming) when you accidentally fall into the water (Or get a cramp or something). As you find yourself in serious trouble, you feel someone grabbing you while pulling you to the surface.