Just as you have insurance for your car, your boat also needs one and do not think that just because you are on the sea, accidents will not happen, they may happen and you need to be ready. There are different kind of boat insurances: total, basic and personal and the policies and guidelines varies depending on the country you are from. If you are in the USA, check out this link of this company who offers marine insurance and also provides with information about the matter:
https://www.boatus.com/insurance/policy.htm
How important do you think is to get a boat insurance?
I would think it is a necessity to get boat insurance, especially since coastal areas where boats are located are most susceptible to natural disasters such as hurricanes and tsunamis. Boats are not cheap, and insurance is needed to protect such an investment.
I wouldn't feel very happy being in a boat that wasn't insured. To my mind, it is just as dangerous if not worse than travelling in a car, and nobody in their right mind would travel in a car without adequate insurance.
We have to have insurance for all types of sailing vessels here, and different policies for each one.
My Son and Husband have a kyak, so they both have to have insurance for those, whether they be going out on a canal, lake or sea, it makes no difference, you still have to hold valid insurance before you go out in them