I saw this in the January 2018 Sea Magazine:
Customs requirements Relaxed
The Canadian government has relaxed the rules for US boaters crossing the Canadian border by water. 233), which received Royal Assent in June, changes the requirement for when boaters have to report to Canadian Border Services Agency (CBSA) officers. Instead of calling Canadian Customs to report in as soon as they arrive in Canadian waters, US boaters need only report to customs when they anchor or arrive on Canadian shores. A day outing that involves no anchoring or “contact with a conveyance” can be conducted without a customs check -in. Canadian boaters still have to report to US Customs, as there is no reciprocity yet.
But I looked it up on the Canadian Customs web site, the above does not seem to match. Above would lead me to believe that so long as you don't anchor or go ashore you do NOT have to report into CBSA. But when you read below from the CBSA site (I have highlighted it) it would appear you still have to CALL in, you just don't have to report to a telephone call in site.
1.2. Program Description and Objectives
Private Boat Processing
All travellers arriving in Canadian waters by private vessel must self-report to the CBSA. The owner/operator of the vessel is required to proceed to one of 428 Telephone Reporting Sites/Marine (TRS/M)Footnote 5
and contact the Telephone Reporting Centre (TRC)Footnote 6
to report their entry into Canada. Only private boats carrying 29 people or less can report through the TRC.Footnote 7
Alternatively, private boaters may report in-person at one of ten Direct Reporting Sites (Marine), which are CBSA-staffed marine ports of entry (POEs).
If certain conditions are met, private boaters may also be able to report directly from the water to the TRC. For instance, travellers arriving from the United States by private boat may report directly from the water upon entering Canadian waters if they do not intend to land on Canadian soil nor leave any people or goods in Canada. Canadian private boaters may also report directly from the water when returning to Canadian waters if they have not landed on U.S. soil and have not taken on any people or goods while in foreign waters.
Regardless of the method used to self-report, the owner/operator of the boat is required to provide all crew and passengers’ names, dates of birth, citizenship and residency, and declare all goods being imported to Canada. The TRC officer records the information in the Telephone Reporting Centre System (TRCS) and then makes a decision whether to release the vessels and all travellers or refer for a secondary examination.
Boaters enrolled in Trusted Traveller programs (e.g. NEXUS) have access to 22 additional designated reporting sites and advance notification privileges not available to other private boaters.
Once a private boater has been referred for secondary examination, a marine verification team may be tasked from the responsible POE to the TRS/M where the private boat is docked to conduct their examination of the passengers and/or vessel, as required