We live in the Midwest & my daughter's birthday is in January. For her 4th birthday we had an indoor beach party at our house.  The children were instructed to wear swimsuits or shorts. As the children arrived I secured a strip of Velcro to the gift they brought and the gift went into a empty plastic wading pool. Later, using a Velcro "fishing rod", each child fished out the present they brought and presented it to my daughter. We had a scavenger hunt for shells (bars of soap shaped like shells), which the children could keep (keep extras on hand to even things out).  The children took turns tossing a beach ball into an empty plastic wading pool and they received their treats in a plastic watering can.  The treats included sunglasses, plastic boats, plastic flower leis, etc.  I decorated with a fish motif and we made homemade ice cream in a coffee can (fill a l lb. can with cream and sugar and vanilla.  Place in a 2 lb. can. Surround w/salt and ice - have the kids roll the can back and forth until the cream freezes).  I put food coloring in the ice cubes and served them in lemon lime soda. The children had little paper umbrellas in their drinks and of course the cake was decorated with a beach motif.  Boys and girls alike enjoyed themselves!