The 23-year-old clocked 2:35.48 in the first event of the morning at the Aquatics Centre, to cut 0.44 off his own record he set at Beijing 2008.
Australia's Matthew Levy set a new Oceania record in second, 2.21seconds adrift, with Croatia's Mihovil Spanja in third.
Garcia-Tolson was honest about where his affections lie and said: 'The pool is where my heart is at.
'I've always been a swimmer but being out there on the track yesterday was amazing, to represent my country.
'The crowd and the stadium were amazing, I'm very blessed.'
He was happy but composed following his world record, saying: 'I'll take that.
'That was a good morning swim. I've been training since Beijing for this and I've just got to get out there and do my race.
'Whatever happens, happens.
'It ended up being a world record so I'm pleased with that but the important thing is to come back tonight and swim it again.'
His was not the only world record of the session, with Ihar Boki dipping 0.47 seconds inside Timothy Antalfy's mark from March in the 100m Freestyle - S13 in 52.08.
Jacqueline Freney was fastest through by almost 10 seconds in the 200m Individual Medley - SM7, Jessica-Jane Applegate of Great Britain leads the 200m Freestyle - S14, Mary Fisher set a Paralympic record of 1:20.89 in the 100m Backstroke - S11, Kelley Becherer tops the 100m Freestyle - S13 and Maddison Elliott heads the 50m Freestyle - S8.
Daniel Fox heads what looks to be a highly-competitive 200m Freestyle - S14, Yang Bozun leads the 100m Backstroke - S11, Roman Makarov is fastest in the 100m Butterfly - S12, Leslie Cameron set a Paralympic record of 2:32.96 in the 150m Individual Medley - SM14, Dmytro Vynohradets laid down a new European marker of 3:01.99 in the SM3 race while Great Britain lead the 4 x 100m Freestyle Relay - 34pts.