This is what I've learnt by watching alot of videos on YouTube of people jumping off cliffs into the water. There are alot of idiots out there.
First. Know how to float. Did you know that it's harder for men to float than women? And that knowing how to swim doesn't mean you can float? Try it sometime. Lie perfectly still on water and see how long you stay on the surface. Practice floating! Why would you go near water if you couldn't float on water or swim. Seems like madness to me.
Second. Watch for currents, waves and rips. Whether you're jumping off a bridge or wharf, off Bulli Point into Lake Taupo or off cliffs into the ocean, the water may be moving and fast. Don't survive the jump or dive just to be carried out to sea on a rip or down the river on a swift current, and ultimately under. Look at the conditions and make a judgment call. It's OK to be smart about this so you can live to make another jump. Look at the water. What's it doing?
Third. There are heaps of other reasons to be cautious about jumping or diving. Is the pool deep enough, are there submerged rocks or logs in the way. Any snags which may drag you under?
Finally, don't jump on your mate. That is so not cool. But you know what is cool. That you've actually got a mate. So give it some time between jumpers. Seriously. You've got a mate, try to keep him! And good on you for hanging out together. Swimming alone is NOT OK.
I'm certainly not the sharpest tool in the shed, but I've seen enough to know that being caution around water and not showing off to my mates is actually OK.
Try to live another day!
It's cold down here