Combining flowers in an underwater environment results in some eye-catching arrangements. Keep the arrangement simple with a few select flowers. The flowers won't last as long as a regular arrangement, because the flowers need to exchange oxygen and carbon dioxide, which doesn't happen underwater.
Vase or Aquarium
Scrub out an aquarium, fish bowl or large bubble vase. Rinse thoroughly and dry. Remove any water marks by rubbing with white vinegar and a paper towel.
Choose flowers that are large and have thick sturdy stems. Hollow stems don't work as well. Small flowers, like gypsophila, have a tendency to come off the stems and float away. Good choices are lilies, roses, iris, orchids and carnations. Bear grass tied in a rubber band adds a bit of greenery.
Cut the stems of the flowers to different lengths. All should be shorter than the vase is tall.
Arrange the flowers on metal frogs. The frog has a flat base with metal prongs sticking up. The prongs hold the flowers in place. One frog is enough for a medium arrangement. Use several frogs in an aquarium. Place a taller flower in the middle of the frog, surrounded by medium-length flowers and finally by short flowers. Pierce the end of each stem by pushing it down on the prongs of the frogs. Push the rubber band of the bear grass in between two prongs. Don't overcrowd the frog. Rinse gently under a spray of water to remove any stains, bits of stems or leaves.
Place the frog with the flowers in the vase, bowl or aquarium. The frog holds the flowers down so they don't float to the surface.
Cover the bottom of the vase with sea glass or glass marbles. Hide the flower frogs with the sea glass as well. If you've used only a few flowers for each frog, work the sea glass in between the prongs to completely hide it from view.
Place a bowl or glass in the vase. Gently pour the water into the bowl or glass until it overflows and starts filling the vase.
Flower-Filled Ice Sculpture
Boil distilled water. Distilled water is pure water and has no mineral impurities to turn the ice cloudy. Boiling the water removes minute air bubbles that also make the ice cloudy. Cover the pot with foil to block any dust from falling in.
Place the flower-filled frogs in the bottom of a plastic container. Cover the frogs with sea glass. Fill the container with the completely cooled boiled water by gently and slowly pouring it down the side of the container.
Cover tightly. Place in the freezer. Freeze solid. Large containers may take 24 to 48 hours to freeze.
Remove the container from the freezer and let it stand at room temperature until the ice sculpture is easy to remove. Place the ice sculpture in a dish deep enough to catch the melting ice.