[header] How to do the dolphin stroke underwater [title] Push off the wall, keeping your whole body under water. [step] Stretch your hands in front of you in a streamline position. Keep your feet and legs straight and together, and keep your core tense. 
[substeps] You should start off low enough in the water that you'll be able to keep your whole body underwater while you execute the stroke. You might need to start off at a slight downward angle in order to achieve this, and it will probably take some practice.