If you look at Screen 12, you'll see a vehicle behind one of the bridge supports, which looks very similar to the vortex out of San Andreas. So if you agree with me in thinking it is the Vortex it looks like Rockstar are doing a lot more on the water aspects of VCS, with the inclusion of the Jetski as well, afterall the water aspect of the gta games since gta 3 hasn't been that major.

The following images are other vehicles that have been spotted in the screens on VCS PSP:

Cuban Hermes, Jetski, Infernus, Squallo, Comet, Speeder, Greenwood, PCJ-600, Sandking, Sparrow, Vortex (not definitively confirmed), Phoenix (not definitively confirmed)