Ideas for wedding centerpieces without glass or candles?

I am getting married on a riverboat, so I can’t have glass items or candles. I am looking for any ideas that could be un-expensive (I’m spending plenty on this wedding already!) I will need 12 altogether. My best idea so far is orchids of different colors, in plastic pots ( My flower is purple orchids, it would be tough to match it) Thank you =)