"It's cold for sure and that will suit our swimmers. They have come out of cold conditions at home and are used to swimming in this," Rush said.
"It is also quite tidal and the current will definitely play a part. Navigation and tactics will be a factor as swimmers go against the tide up the course and back with it."
Rush is predicting stern competition for the New Zealanders with 62 men and 40 women entered.
There are nine spots remaining for men and women to complete the fields for London, with only one swimmer per nation eligible to qualify.
The men's field includes high-quality swimmers like David Davies (Great Britain), who was second in the 10km at 2008 Olympics, and Ossama Mellouli (Tunisia) who won the 1500m freestyle at Beijing.
The women's line-up is also going to be very competitive because the USA have not qualified, so their two best open water swimmers are competing.
"It's going to be very tough but I think we are in good shape."
Rush is hoping for a strong pace over the six laps of just over 1.6km to ensure the race does not come down to a bunch sprint.
"It is certainly our best chance. There's so much riding on this I expect the strongest swimmers will want to set a good pace."
The team have one further light training swim tomorrow before resting up for the weekend with the women's 10km race from 4pm local time on Saturday and the men's race on Sunday.