The 24-year-old Sarawakian finished 33rd out of 36 swimmers in the overall ranking on the opening day of the swimming event at the Tokyo Aquatics Centre.

Only the best eight swimmers will advance to the final to be held tomorrow morning.

Earlier, Welson came in sixth in the second heat after clocking 3:58.25s while Venezuela’s Alfonso Mestre came in first with a time of 3:47.14s, followed by Martin Bau of Slovenia (3:52.56s) and Joaquin Vargas of Peru (3:52.94s).

Germany’s Henning Bennet Muhlleitner topped the overall chart with a time of 3:43.67s while Felix Auboeck of Austria was second best (3:43.91s) and Italian Gabriele Detti third fastest (3:44.67s).

This is Welson’s second attempt in the same event, having clocked 3:51.57s en route to being ranked 34th overall at the 2016 Rio Games.

Welson, however, will have another opportunity to prove his worth as he is set to feature in the men’s 200m freestyle tomorrow, as will Phee Jinq En in the women’s 100m breaststroke.