The cracks may be nothing more than the flex induced in the gel coat when impacted...
Repairing them
may be as simple as chasing the cracks with a rotary tool with a small pointed bit attached and opening them up by creating a sort of crevice to be filled with some gel paste.
The difficulty will lie in the exact matching of the original colors which, even for the experts, can be tricky.
Here on iboats.com you can find several gel repair products...
http://www.iboats.com/Boat-Gel-Coat...8647008--session_id.296095144--view_id.246645
If the hull has any significant flex or give in that particular area, the damage may be structural and require more extensive repairs...
Here's hoping it's just some minor cosmetic damage and wishing the best of luck!
GT1M