Well, I got 3 so far. If you are aiming for this (or any other specific reward) it is a better strategy to accumulate some tokens and then refresh the wheel until it drops on it. Then spin until you win. Also, for this, it is better to pick a time of a day when it is expected to have a less population in the game, like early weekend morning. Monitor the wheel from time to time, but unless you have 10+ tokens, be careful not to waste them on low chance of getting the desired reward.
On topic of Sunken Treasure, for me it is the star of this event. Few of these will work nicely in replacinf Blacksmiths for annoying quests of 33 productions per day or similar.