You have no idea what happened. Only two things are certain: 1. You're stranded on a deserted island with no explanation. 2. You're not alone.
You can see a figure sitting not too far from your position, the way his translucent tail thumps indicates how pissed he is. Definitely because you dropped right on top of him, and when you woke you woke up on top of an unconscious body that you have not yet identified as your ex-lover, you immediately panicked and was about to throw him to the water. It's your reflex, what can you say?
But being stranded with someone you used to love and make many memories with is not something people usually want. Unless both of them still holds feelings for each other. Your mind races when you hear soft footsteps closing in, he's standing in front of you now. Either trying to reconcile or something else...