For my daughters 1st birthday we chose Under the Sea for the theme.  We started planning months ago and were able to purchase most of the items on clearance or sale which helped to make the event inexpensive. For invitations we went to Micheals craft store to purchase paper stock that had under water scenes.  We chose paper stock with Orca whales, dolphins, tropical fish and coral reef.  The text of the invitation read "Under the Sea, Under the Sea come celebrate turning One with Me" and my daughter name underneath, Departure date:(date), Dive Time(start time), Resurface Time(stop time), Port(our address) and S.O.S (our phone number). I received several compliments from our guests on those. We hung fish net on the deck outside with plastic sea creatures in it to welcome our guests to the party. We decorated with Ice Blue, Aqua, Periwinkle, and Royal Blue streamers throughout the house.  We covered the table with blue table cloth and celaphane to look like water.  We hung paper cut outs of sea creatures and plastic sea animals (star fish, crabs, tropical fish, seahorses, lobsters, etc.) in the windows and then hung the stramers in front of them so it appeared as if they were swimming. We had the party in our basement to coincide with under water, we put streamers on the walls and ceiling to help with under water effect. We also had paper cut outs of fish and sea life on the walls and hung more plastic sea life from the ceiling. We purchased some fish net and put some on the ceiling with starfish and shells in it, and hung some on the walls with more sea life in it. I found small blow up fish through Oriental Trading company and blew those up, the smaller children enjoyed playning with those while the older children played some games. Upon entering the "Sea" we had created the kids were given a pail(that we purchased from the local dollar store) for them to put their "treasures" in. Each bucket contained a small bottle of bubbles that had under water theme around it, a beach ball that we purchased on clearance at Target, and pencils with erasers that were either Dolphin or Orca Whale themed. For the smaller children we put packages of Goldfish crackers and small plush sea animals that were purchased from the Oriental Trading Co.  All of the kids loved their buckets and were a big hit with parents. It kept the kids occupied and the adults were able to visit.  We served Green and Blue Kool Aid from Shell shaped punch bowls that we purchased from Oriental Trading Co., For food we served sandwiches that were displayed in Fish shaped bowls and salads from shell shaped bowls. We purchased smaller clam shell bowls for the pickles and olives.  The salads were pistachio(green) and fruit salad, we added blue food coloring to it.  My sister made a shell shaped cake with smaller shell cakes around it, enough to spell out "happy 1st Birthday" it was beautiful. For games we kept it simple, we had children that ranged in age from 1-9 so we had to be creative. We buried the goodie bags in the sandbox outside and the kids and to dig until they found a bag, this was fun for all ages, it got the kids outside and helped to wear off some .  Next we did the Fish Pond. I hid in the shower stall and my husband came up with creative ways to tell me who was next in line and the kids were given a fishing pole to throw over the top of the shower, at the end of the line instead of a hook, there was a clothespin, I "hooked" the prize and tugged on the line and they reeled their prize in. Prior to the party we had purchased a gift for each child that would attend the party as they were all neices and nephews it made it easier for us. Every one had a great time and the kids really enjoyed being able to open their gifts, it helped to keep them from wanting to open the birthday girls gifts. Everyone said they had a great time and can't wait to see what we will come up with for the next one. We had such a great time planning this party, it does take time and planning and organization but it was very easy to find what we needed once we had a plan. We are already thinking next year.