Surfing Waves

Do you have to put a LOT of pressure on the tail of the back of the board to do a quick turn?

Ta

Sometimes, yeah. Are you talking about turns so tight you're surfing just on the rail?

My boards are pretty lively, so basically I just even think about turning and it turns. A little backfoot toe or heel pressure, eyes and shoulders anticipating where you're going or your next move, sometimes a hand in the water, and you're good.

Maneuverability depends a bit on your board and fins setup too.

What size board. Also, does yours have a stomp pad?

think about turning like on a skateboard.

Its a 6'11'', tri fin shortboard

Speaking as someone who is superbly qualified to tell you the technique of snappy turns....
(ie, someone who is a bit rubbish at them, so spends a lot of time thinking about it)

It's not about a huge amount of pressure, but more about well-placed and well-timed pressure. If the board is moving with sufficient speed and is planing properly, it'll be almost floating above the water, and that little bit of pressure will raise the nose up out the water... and then the critical timing to have already begun the turn with your body comes into play.
Putting too much pressure on the tail will stall the board unless you're planing very fast.

A 6'11 board will be kinda tricky to do a really snappy turn with. Not impossible, but you'll really need to put the effort into the turn.
To start with, go for the stomp on the tail, and a really big swing of arms/shoulders. You'll turn, stall, and then fall off, but then you've got the basic idea to iron out the details.