This is correct. Water has an extremely high heat capacity, meaning that it takes a lot of energy to warm or cool it by any noticable amount. Land does not. So while the different amount of sunlight in summer/winter changes the land temperature by a large amount, the ocean barely changes. Most of the land on Earth is in the northern hemisphere and therefore we get those temperature swings.
This is correct. Water has an extremely high heat capacity, meaning that it takes a lot of energy to warm or cool it by any noticable amount. Land does not. So while the different amount of sunlight in summer/winter changes the land temperature by a large amount, the ocean barely changes. Most of the land on Earth is in the northern hemisphere and therefore we get those temperature swings.