If you had regular job, you were eligible for unemployment there was also PUP enabled due to pandemic, so if you were self employed you could request unemployment under that. In addition there were also short periods of time where you could get extra $600/week (as it is impossible to survive for long on the usual unemployment amount)

They tend to work as contractors on a limited term contract and intercalation maritime labor laws are unlikely to require it. Note also the country of registry for the ships may have more lax labor laws too.