Have they? And how many of them can be ordered to surface under tide power, for easy maintenance access and towing into a maintenance dock without involving exp

Have they? And how many of them can be ordered to surface under tide power, for easy maintenance access and towing into a maintenance dock without involving expensive divers? I presume the tether on this would be built long enough for controlled surfacing, a longer tether means larger deadzone between inbound and outbound tide, but there won't be much energy in the flow close to the turning point anyways.