Thirty feet is GREAT! Well beyond many many people's abilities. Not sure if you're aware of it, but you're doing better/more than 90% of all snorkelers. I've been on snorkeling trips in Mexico a few times, and noticed that I'd be the ONLY one on the boat that actually freedived. Everyone else just snorkeled on the surface. Nothing wrong with that, but OTOH it's cool when we're all back on the boat and everyone starts asking me questions. "How deep can you go?" "How long"? etc.
I tried it in once in Florida, but they insisted I wear a vest and to not dive down.
OTOH, I'm not all that great when I compare myself to guys that live on a coast and get to do it all the time. Heck, I've only been to forty max, and that's by jumping in while holding on to a cinder block so I didn't have to kick my way down. And I was only good for one minute, thirty seconds. But if I dive into a pool and hold myself down by holding on to the drain grate, I'm good for two minutes and eighteen seconds before I start seeing spots (just did it last week).
I envy those dudes that go down fifty feet and spear a tuna. That's gotta be a blast.