Stroke Development. 5-10 yrs. Must pass Level 2. Skills include: front crawl stroke, rotary breathing, elementary backstroke, scissors/dolphin kicks, treading, sitting/kneeling dives. To Pass: enter chest deep water, swim front crawl, maintain position by treading or floating, swim elementary backstroke. NOTE: in most cases, it will take a child more than one session of lessons to pass the level.