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.
Stunning Fire and Ice themed Prom! This is sooo pretty!! http://facebook.com/moncheriprom