Yeah, and be real careful when using Y-adapters that plug
into 50A/220VAC shorepower. There is a very real danger
of meltdown if you're not careful
Each of those 30A female connectors can be overloaded without any shore power
circuit protection. The breakers on the dock
are 50A. Depending on how your boat is wired, it's quite possible to try to pull 50A @ 120VAC through EACH of the two 30A cords. This would cause a meltdown and, quite possibly, a fire.
Remember, in any case, that 30A connectors are not really capable of carrying 30A continuous. They are a horrible ancient design and unless brand new (both the cord ends and the receptacle ends), polished, tight, and correctly connected they will heat up with a 30A load. Much better to rate them at 24A maximum, and keep them clean and tight.
Moreover, should you lose a neutral due to a loose wire, corrosion
, breakage or burn, etc., you could have 240VAC on a 120VAC boat circuit. That tends to spoil your whole day, not to say what happens to your 120VAC appliances