We recently completed the first week of a 2-part VBS. Here are some of the decorations. Like the bubbles? We made them by soaking paper with water and then dropping blue paint onto the paper. See the picture below. Then we cut out different sized circles when it was dry.
They hung a gauzy material from the ceilings to replicate water and put black silhouettes of sea creatures above it.
I love the coral they made from pool noodles and Great Stuff (the spray insulation foam you can buy).
There were swarms of fish everywhere. The older ladies in the church loved cutting these out.