Agreeing with everyone on the whole breaking standards issue, but in reference to your specific question, I have found that on surface swims split fins have worked better for me personallya nd for may of my students. If you are in warm water then use full foots, so much easier and lighter. If its not a stand alone swim test that they are making you do (?!) then go with what ever equipment you own so that you are more comfortable and familiar with it, plus realistic.