I mean, who is going to know or care if you're transmitting on SSB band with an opened up ham radio, as long as you have the proper licenses, permits, use correct radio protocol, and otherwise follow 'the rules'?

I've often read/heard about this, that it's not legal to operate a ham radio on the marine frequences --but, in practical reality, does anyone really care, as long as you're licensed and know what you're doing? I don't see how anyone would know or care what kind of radio you're using to talk with on the marine bands...but maybe I'm missing something?

Is there a different type of licensing requirement for SSB vs. ham?