Poem 'Fading' (last one needing feedback)

I’ve been writing a fair bit of poetry lately. This is the last one I would like your opinions on. The rest of them I’m going to keep to myself. I had someone read this and say I need to better explain exactly what is going on? I don’t know, have a read and let me know your thoughts :)

Fading

Down at the deep blue lagoon she waited, hoping to see him soon. He had promised to show when the sun was still bright, but the day was slowly fading into night.

As she cast her eyes across the sky, she searched for reasons but could not think of why he would leave her alone in the cool sweet air. Why the minutes were passing and he still wasn’t there.

As the night grew cold a tear fell down her cheek. She slipped into the warm water and her heart grew weak. Through the crystal lagoon she began to swim, and all she could think of was her deep love for him.

She soon felt a presence and quickly turned around. Her one true love she had finally found. But she could see that something was not right - his dark sillohette was now pure white.

She let out a sob and swam to his side, not wanting to believe that he had just died. She held out her arms and embraced him tight. He kissed her gently and slowly faded from sight.