Here is the low down :
The best returns in slots are in Las Vegas...some machines actually post a 101% payback...most are between 95%-99%.. In Atlantic City pay back is less...in areas of 85% - 99%...all depends on which casino you gamble at..In order to change the % on a slot machine in Las Vegas or Atlantic City they must get approval from the Gaming Control commission...The item they change is the RNG (Random number generator) This little black box inside the slot machine spews out number combinations at a rate of thousands per second...The symbols on the machine are meaningless,they are for show only...the winning or losing combination is actually in the little black box...when the black box stops spewing out numbers after you put your coin in the slot the results are know instantly by the slot machine then the symbols that correspond to the number in the box show up on the pay line. The higher the payback the more winning combos come up in that box...the lower the payback the less winning combos come up.
Ever notice that many times you miss the jackpot by one symbol...that is called the hook...many combinations of numbers represent symbols that miss the jackpot by one reel.
At sea on a cruise ship the company that runs the casino does not have to report to a gaming control comission. They can set their own odds usually around a pitiful 60% which means they on average keep 40 cents for every dollar played. Of course some people beat the odds, but for every winner their are many times over losers.
Consider playing slots on a ship or anywhere for that matter a form of entertainment..and the price you pay for that entertainment is the loss at the machine.