CAn i lose my job or not be covered for injuries incurred at a Company A Team Building Activitiy

My boss from Company A is requiring us to participate in a whitewater rafting "team building activity" that has a waiver of liability, hold harmless from rafting company for me to sign - stating "you could die", also my company is requiring me to sign a waiver releasing them of all liability. it includes a statement that no work benefits will be paid if I am injured or disable, as this is not considered work related. I recently declined, and my boss send a email, indicating my non-participation will have effect on the team...... I feel pressured as I feel by not participating i may lose my job...and deathly afraid of white water