This is what the official strategy guide from Dreamcatcher says:
WARNING - SPOILER!!!
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
You said you had refueled, so I'll start from there.
Further along, your way is blocked by 2 water buffalos. Try to go forward using the forward arrow through your windscreen. One of the water buffalos will attack the hydrafloat (ie, boat) and damage the engine. (I placed the forward arrow on the window [what the manual calls the windscreen] in front of me, just above the boat's console.)
Turn to the left of the windscreen and click to turn the craft. You now have access to the console again. At the display, select grapnel. It will go into active mode. Your cursor icon will turn into a grappling hook.