Drugged on Deck by Susan Harper

Hope is back on the cruise ship, working anywhere they need her.  She has hopes of becoming the event leader because the person holding that position is getting ready to retire.  Then she learns they are giving it to a new guy who doesn't even work in the ship!

He tries to be friendly but all he does is get in her way.  She tells him to leave her alone.  Fellow employees tell her she's rude.  Then they remove her from the dining hall for a while becuse she fought with him in there.

So now she's being a lifeguard.  She has the big family she served in the dining hall down swimming.  Then she notices one in the bottom of the pool.  She goes to rescue him, does CPR and gets him breathing again.  Then he has a seizure and dies.

The doctor says he's been poisoned.  It's not an accident, it's murder...

He was the only son in the family.  His father is broken up over his death.  Did one of his daughters kill their brother?

Hope digs around asks questions and eventually figures it out.  Can she stop the murderer (who plans to kill again) or will the murderer stop her?