If you are doing a quilt about 45" square I would use my favorite "Speedy Baby Quilt II".
http://schoolgirlsamplers.com/pdftut...peedyBaby2.pdf
The 16 1/2" center square would be great for the dolphins, maybe a blue batik for the 1st border, and pick up the different colors in the 5" charm squares. The sand and sea shells would be great for the outside border and use the dolphin fabric again for the corner squares.
I hope you show pictures after you decide and finish it.