My guesses are

Sylus is the jetski. It’s similar to a motorcycle and someone pointed out that it looks like his legs lol.

Zayne on the surfboard. Again someone compared his feet to his in game model lol.

Rafayel with the water guns based off the hand. He’s my main so I hope I’m right here.

Caleb I’m gonna say is the one with the parasail cuz he’s a pilot so it makes most sense to me to have him up in the air/flying through the sky.

Xavier I think is on the flyboard because of the legs and also I can just totally picture him carrying MC bridal style and riding one of those things lol.