SUNSHINE Coast swimmer Guy Harrison-Murray went out fast in his S10 400m freestyle heat.

Although he finished third, he qualified for the final as the fifth-fastest swimmer.

"I'm really happy and surprised with the time,"  Harrison-Murray said.

"It still felt like a heat swim and hopefully tonight I'll have a little bit left in the tank."

Harrison-Murray said the plan was to start relatively quick.

"I talked to my coach and we knew it was going to be a quick time to make the final, so the plan was to take it out pretty quick and then depending on where I was at the 300, see where the rest of the field is, and then decide in that last 100 what I do from there," he said.

This is  Harrison-Murray's second final, he was in the 50m freestyle last week, where he finished seventh.

"I'm hoping the final will go well, I'm in a good lane," he said.

"It will be a really interesting race."

Fellow Australian Rowan Crothers also made the final, snatching the last qualification place.

He said his plan was almost the opposite to  Harrison-Murray's, with the idea to finish fast, and take the start a little easier.

The final is at 6.57am Friday morning, Australian time.