Just hours before a 31-year-old motorcyclist was thrown from his bike to a "nightmare" death in the Brisbane River, he shared his twin fears of drowning and falling from a great height, his sister says.

Dean Jagger was riding through the Brisbane CBD about 10.20pm on Saturday when he lost control on the ramp to the waterside Coronation Drive, crashing into the barrier and flying into the river.

Dean Jagger died when he was thrown from his motorbike into the Brisbane River.

His grief-stricken sister Tracy took to Facebook on Sunday to post a series of tributes to her brother and lash out at the pub where she said he had been drinking and lost about $2000 on poker machines before the crash.

“He was telling Rolf last night how drowning would be the worst way to die,” she wrote on Facebook.