35 ILCS 158/15-5
For the purposes of this Law:
"Department" means the Department of Revenue.
"Purchase price" means the reasonable consideration paid for a watercraft whether received in money or otherwise, including, but not limited to, cash, credits, property, and services, and including the value of any motor sold with, or in conjunction with, the watercraft. Except in the case of transfers between immediate family members, reasonable consideration ordinarily means the fair market value on the date the watercraft or the share of the watercraft was acquired or the date the watercraft was brought into this State, whichever is later, unless the taxpayer can demonstrate that a different value is reasonable. In the case of transfers between immediate family members, reasonable consideration ordinarily means the consideration actually paid, unless it appears from the facts and circumstances that the primary motivation of the transfer was the avoidance of tax.
"Watercraft" means:
35 ILCS 158/15-5