RedactedNarrative: Operator launched V1 from Springhill Park below Trimble Lock and Dam.  V1 would not start while floating down river and the operator noticed V1's engine compartment was taking on water.  The operator and passengers used skis to paddle V1 to the bank.  V1 continued to take on water until the stern was submerged and came to rest on the river bottom.  V1's bow was above water and they were able to tie it off to tree roots on the bank.  When V1 was removed from the river on 08/26; it was noticed that the plug was missing.  The operator failed to notify anyone of the accident and he did not have the required insurance on V1.