Like others have said, tugging seems to be highly impractical. If you'd really, really, really want to try anyways, you might perhaps habe an easier time with e

Like others have said, tugging seems to be highly impractical. If you'd really, really, really want to try anyways, you might perhaps habe an easier time with electric ships that are fully capable of going alone, just without enough battery for the whole way. And that can be take-extended on the go by a relay of battery boats supplying electric power via cable instead of some very high number of Newtons (battery boats would only carry enough engine to self-supply). But close formation in heavy weather would still be so hard that it might in fact be easier to "simply" make them all submarines... (yellow, presumably) But we shouldn't start juggling around absurd amounts of batteries as long as we don't even utilize low hanging fruit like equipping all those cargo haulers with mighty propulsion kites. That's basically a solved problem, just not happening because the refinery waste ships are conveniently incinerating is still too cheap. Particularly as long as we still burning fossils for electricity on land. Ship engines operate much to optimal load than ICE car engines designed for a market that demands excessive peak power for short bursts of acceleration. The carbon break-even point for ships would require much cleaner electricity than that for cars. Cars are an absolute outlier because their cruise load is so much lower than their advertised power and ICE engines are almost comically inefficient at low load fractions.