Does ocean-going capability separate ships from boats?

Can ships and boats be distinguished by whether they are ocean-going?

Not reliably; many vessels called boats go to sea, so the carried-craft tradition is a more useful historical explanation.

An ocean-going distinction between ships and boats runs into the example of fishing boats. Many of them routinely operate at sea. The traditional naval-architecture relationship between carried boats and carrying ships offers a better historical explanation. Naval categories often preserve institutional convention rather than a universal physical rule.