For my son's second Birthday party we had our usual pool party.  Invites for children were on beach balls & for adults w/o kids I printed out invites on scrapbook cardstock & had my son paint it.  Then I cut it out in the shape of a fish. Decorations outside were Christmas lights, 8 fish shaped & 1 seahorse shaped balloons, and a boat shaped pianta.  At the gate to greet the guests was a motion detecting singing lobster. Inside were birthday banners (2) - one for each year - and plastic fishes hanging from ceiling and walls. I also had palm trees and boats and more balloons attached to Oriental Trading fish wrapped bubbles. Cake - I saw the idea on a magazine (forget which one) - blue icing with plastic sailboat on top with teddy grahams in bathing suits swimming.  Side of cake on bottom was crushed graham crackers to look like sand & green fruit roll-ups shaped like seaweed. I used more teddy grahams with icing bathsuits swimming & gold fish crackers in schools.  I used gummy lifesavers to be lifesavers too.  I made individual cupcakes with individual icecream for kids -easier to serve. Activites - sandbox, swimming, freeplay in playroom, and pianta.  Party favors included balloon with bubbles & bucket with shovel and sand toys (found at dollar store. Dinner - hamburgers, hotdogs, chili, fruit salad, macaroni salad, potato salad, chips & dips, etc. Drinks - sodas, juice boxes, etc. I hope this helps with your next pool party.  I really recommend the beach ball invite & write have a ball on it. A great way to get kids excitted!