^^^^ excellent advice ^^^^
I grew up free diving or back then it was known as snorkelling, pretty much every day after school I would go on my own (not recommended at all) and on the weekends with a friend. The sea was warm so surf shorts were enough.
Lots of years later, the wrong side of 40 and living as from the sea as you can in the UK I decided I wanted to see what I was capable of if I pushed myself a bit so I got myself fit and did a weekend course at a 10 story tall submarine escape training tower.
I could easily hold 2 minutes (this is considered a short time in free diving). Over the weekend with the help of a mono-fin and gradually building up confidence I managed to get down to the bottom of the tank which was a 100ft deep and more importantly back up safely to the surface.
https://www.youtube.com/watch?v=Kr05eCmeorI
Please, please as mentioned do some training, learn some techniques and take it slowly as shallow water black out can hit you without warning and if your buddies don't know what to do when it happens or don't spot you're in trouble you are dead, simple as that.
Don't want to put you off as it is a great sport to do and a lot of fun if done safely