If it is any consolation, this type of "accident" occurs with parked cars as well.
I will presume that your boat is insured. If it is, I will presume that it is aware of the accident because your boat, which was hit twice, must have sustained some damage. Contact your insurance company and provide them with details about the accident and the lawsuit. This is one of the things you pay insurance premiums for. Your insurance company will defend you and handle the lawsuit.
If you do not have insurance, then you will need to hire an attorney immediately before any more time passes -- you have a lawsuit to defend against the party suing you but you also have a claim against the owner of the boat that started this watery version of bumper cars.
I agree with my colleague that you should immediately contact your insurance company (actually, you should have do that right after the accident). If you don't have insurance, retain a lawyer right away. You say the amount sought in the suit is large, this will not go away by itself. Good luck.
I have been licensed to practice in the State of Oregon since 1990. I am not offering legal advice regarding your question, only general information regarding the law. You are not my client nor am I your attorney unless we sign a retainer agreement.
This type of situation may not be dischargeable anyway. Get immediate legal help to defend the suit. Many factors go into the defense, including whether the boats were docked, being driven, with your authority, or not, stolen, drinking or narcotics, any personal injuries, etc. Just like automobiles. And for goodness sake, do not talk to any more people about the incident, except your carrier or attorney.