Here is the full list of all 24 Riptide GP2 trophies - there are 6 bronze, 11 silver, 6 gold and 1 platinum.
All Trophies Unlocked
Get 3 stars in all Career events
Earn 3 stars in every Race event
Get 1 star in all Career events
Get 2 stars in all Career events
Earn 3 stars in every Hot Lap event
Buy 8 hydro jets
Earn 3 stars in every Elimination event
Earn 3 stars in every Freestyle event
Get 2000 points in a Freestyle event
Reach level 20
Buy 4 hydro jets
Buy 1 hydro jet
Jump over 200m
Get 1500 points in a Freestyle event
Unlock a level 10 stunt
Get 1000 points in a Freestyle event
Win a race without the rider
Smash a bridge in the Factory Shift event
Find the hidden easter egg
Upgrade a hydro jet fully
Paint your hydro jet
Upgrade a hydro jet
Place 1st in any event