To be sure, Wednesday's agreement brokered with Raul Castro does not end a trade embargo with the country and does not yet open the country for tourism. Those changes would need action by Congress.
But always looking six months to a year ahead, traders aren't waiting for any official changes before betting on the shares.
"A lot of people are going to want to go home, and a lot of people are going to want to visit Cuba," said Rhino Trading Partners' Michael Block. "Hotel companies will have a chance to build there."
The Cuba news boosted shares of Carnival and competitors Royal Caribbean and Norwegian Cruise Line Holdings to near new highs for the year.
"All three of the cruise lines under our coverage (Royal, Carnival, Norwegian) have a considerable amount of capacity operating in the Caribbean, and we believe an opening of Cuba could generate material incremental demand, both from repeat cruise customers and those new to the industry," Stifel analyst Steven Wieczynski wrote in a note to clients.
Carnival said in a statement to CNBC:
"Cuba is the largest country in the Caribbean, so there's some exciting possibilities from a cruise industry perspective. Some infrastructure for cruising already exists in the country, along with several ports, so it offers great potential, but there are other issues that will need to be taken into consideration if this market opens up."
Normally, about 25,000 shares in the Herzfeld Caribbean Basin Fund change hands. Early afternoon Wednesday, volume was greater than 19 million.
The fund is "focused specifically on companies that are poised to benefit from the resumption of U.S. trade with Cuba, once the U.S. embargo prohibiting trade with that country is eased or lifted."
The "CUBA" fund's largest holdings are Copa, Coca Cola Femsa, Seaboard Corp, MasTec, Lennar, Royal Caribbean and Watsco Inc.
Read More Obama opens door to new relations with Cuba
Wednesday's announcement comes as no surprise to the managers of the fund, Thomas Herzfeld and Erik Herzfeld, as they wrote the following in the fund's annual report posted in June:
"Extreme inflation and rapidly increasing poverty have led to continued economic and political volatility in Venezuela. This, coupled with plummeting oil exports and declining production levels for the nation, may force Venezuela to reconsider its policy of supplying subsidized oil to Cuba. As a result of this pressure on its economy, the Cuban regime may be more amenable to U.S. diplomatic overtures, even though relations between Cuba and Russia have been warming."
Investors should be cautious when seeking plays related to normalized Cuba relations. While the aforementioned companies and funds have a legitimate chance to profit from a free Cuba, some of the securities moving on Wednesday do not have much to gain.
For example, shares in the Cuba Beverage Company jumped more than 100 percent to 4 cents a share midday Wednesday. The stock, which trades over the counter, has a market capitalization of just $3.7 million. Going by the company's website, it has nothing related to the country other than its name. The maker of "herbal energy juice" is based in San Diego.