曼哥，秋MM，翻译诗词容易，翻译意境很难。我只能试试，请斧正。

假如，你是只小鱼/If you are the little fish
我愿做那海草一片翠绿/I’ll surround you with tenderness, like green seaweed
在辽阔无边的海域/In this endless sea
戏嘻/play with you
呼吸/breathe with you

假如，暴风雨来袭/The storm is coming
也许那是你伤心的泪滴/Perhaps that is your tears， with sadness

 我不会离你而去/Never leaving you alone
深深潜入海底/ I’ll go a thousand miles deep
永远相伴相依/Forever, standing by your side