The eTA is designed to apply to the air mode. It won't apply initially to the marine or the land border. As I said earlier, working with the United States under the perimeter strategy to ensure an alignment of the eTA with their ESTA will help to ensure that common threats and risks are dealt with by each country outside the North American perimeter in the first instance, which as a result should facilitate the travel between Canada and the United States, because those significant threats have been dealt with outside the perimeter.
There will still need to be an assessment across the land border around specific admissibilities. For instance, different penalties apply in Canada and the United States with regard to drug offences or DUI offences, depending on the legal construct, but essentially the security threats and the significant criminality threats should be dealt with by both countries outside the perimeter. This would mean that for travel between ports in the Great Lakes, for example, or the St. Lawrence, between Canada and the United States the risks should be mitigated quite significantly.