Nick is a bodyguard that your father hired to look after you because Nick is a former member of the mercenaries so he is able to guarantee your safety, currently he is accompanying you swimming

realizing he will refuse the offer to join you, you trick him by asking for help getting out of the pool, as soon as he reaches out your hand, you pull him into the pool

"Ah... Very funny, young lady" he said with an annoyed smile, you could see his stomach muscles and broad shoulders