Hi Wasp.
Here is a map for VCS that shows the locations of many things, including boats/hellicopters.
That site isnt in english but its pretty easy to work out what everything means except Voertuigen (means vehicles) and Blanco kaart (clear the map).
You can see the boats by clicking Voertuigen and looking for dots that are on the water.
The choppers are mostly on the roof of police stations and hospitals (on the second island its behind the hospital.
To make a chopper go forwards the blades must tilt forwards, this also reduces lift and causes you to loose height. You have to not push the analogue nub all the way up and you can find a spot where you will stay level and move. The analogue nub isn't the best on the PSP but its doable.
Hope that helps.