Rush established his greatest marathon swimming legacy in the English Channel. He swam the English Channel in 1985 in a single-crossing and then set a double-crossing record in 17 hours and 56 minutes. He made successful one-way crossings in 1986 and 1987 and then became the second swimmer to achieve a three-way crossing in 28 hours and 21 minutes included a first leg of 7 hours and 55 minutes which was the fastest swim of the year. In his epic three-way crossing, he swam his first leg in 7 hours 55 minutes, which was the fastest swim of the year, his second leg in 8 hours 15 minutes to set a double-crossing record, and his third leg in 12 hours 11 minutes for a triple-crossing record of 28 hours 21 minutes. Rush completed his tenth crossing in 1988.
His list of notable marathon swims is here.
Rush is currently the national open water swimming team head coach of New Zealand and assists swimmers from around the world tackle the treacherous Cook Strait between the North and South Islands of New Zealand.