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
Buy 8 hydro jets
Win a race without the rider
Find the hidden easter egg
Get 3 stars in all Career events
Earn 3 stars in every Hot Lap event
Get 2 stars in all Career events
Get 1 star in all Career events
Earn 3 stars in every Race event
Earn 3 stars in every Freestyle event
Buy 4 hydro jets
Reach level 20
Earn 3 stars in every Elimination event
Jump over 200m
Get 2000 points in a Freestyle event
Upgrade a hydro jet fully
Smash a bridge in the Factory Shift event
Get 1500 points in a Freestyle event
Unlock a level 10 stunt
Get 1000 points in a Freestyle event
Buy 1 hydro jet
Paint your hydro jet
Upgrade a hydro jet
Place 1st in any event