Submerged arrangements like this can be stunning and cost effective. We could do a mixture of something like this, only as you suggested, with more vases (I think 5) on each table, for half of the tables, then fuller low centerpieces for the other half. And candlelight all around! Also, these could be repurposed to line the aisle during the ceremony.
Simply inflate a ballon, wrap several sets of thread or yarn around it, and spray fabric stiffener all over. Once the thread has dried completely, simply pop the balloon and you're left with a gorgeous, unique wedding decoration.