Any activity involving an increased risk of injury can be considered a hazardous activity.
Such activities (or any sports on a professional basis) will not be covered under your policy unless declared to and accepted by the insurer at the time of taking out the policy. Most often an additional premium will be required.
You should ensure that you have received confirmation in writing (on your certificate) that you are covered and you have accepted any special terms or changes in cover imposed by the insurer.
There are usually additional conditions applicable to all levels of Hazardous Activity;
i) All participation in any activity must be on an incidental and amateur basis unless specifically stated otherwise in writing on your certificate;
ii) All appropriate and recognised safety equipment and training must be utilised;
iii) Increased medical excesses applicable under the hazardous activities sections are not usually waived even if you purchase the excess waiver option.