Cay to the city island is so hard to unlock, I need advice !!!

I'm not aware of any cheats or mods to help. I think giving CPR on the beach might help with the points required for something, but not rescuing drowning sims. I did this a few years ago and found it tedious but had a large household of sims to keep me occupied. Then when my sim finally got the award the badge wasn't achieved. I was after badges at the time. I then discovered that points towards badges are awarded randomly to sims from the household, so it is almost impossible to get most of the IP badges with a multi sim household. So I did it all again and made the video series 'Caroline and Friends' where she got all of the remaining IP badges for me by being a single sim household. I'm not sure if this is relevant to what you are trying to do but thought I'd mention it just in case you are trying for the badges. I know when she finally got to achieve that Cay to the City achievement it happened suddenly and unexpectedly. I used to send her to several different beaches each shift. I don't remember much else about it.

Good luck with your progress.