Hello, I have just bought a mavic air and I can’t wait to get flying properly.. just wanted to ask if there’s anything I should look out for in my settings?

I’ve seen a few videos where drones have automatically landed by themselves in water.....

Hi, thanks for reaching DJI Forum. We do appreciate bringing this query to us. Please refer to our YouTube tutorials for a better understanding of our aircraft. Thank you.
https://www.youtube.com/playlist?list=PL65kukZorPdMj0Uh22SeX-_Jyb_dMJEss

Just to add, read the manual front to back so you can better understand the terminology and Welcome to the DJI forums. It's National Aviation Day!

check your RTH altitude in your settings. ensure that is set to an altitude that is higher than any obsticles in your flight area (eg; trees, buildings mostly).this next tip is not in settings but is a preflight internal procedure which if you do not allow to finalise ie:take off before it is finalised, then such mishaps like landing in water becomes more likely.
Do not launch or take off before the top icon bar on the left side has gone to green.  
if taking off before this bar has turned green then it is likely you will be taking off before the home point has been accurately recorded.
wait for the top bar left side to go green and hear the voice recording say : Home point has been updated - please check it on your map.

welcome to the forum, start in an open area, no trees, stay clear of water and other challenges in the beginning and like the others say, read the instructions, happy flying

....and i repeat, read the manual front to back

Welcome to the forum. Make sure you have enough sat before taking off.
Be sure to read the manual

And... read the manual. No seriously, leave the drone sitting on the table and go read the manual first. Then watch all the videos on setup, initial configuration of your drone, how to care for the batteries, etc. before you do anything, You'll thank yourself later.

Oh, and welcome to the forum.