Note the test methods, but for most, yes, they are equivalent. Check out the list of methods: https://www.hach.com/wah

Methods will note if they are appropriate for seawater (non-significant interference) and meter-specific procedures.

Have you asked Hach? I found them willing to give detailed replies to ensure that you got the most appropriate test kits from them.

It is best to ask the manufacturer if it can be used in seawater, although the manual states that a silicon photodiode detector is used, although it does not specify the serial number, I send you several articles where the silicone detector is used to determine various parameters in marine water. https://www.sciencedirect.com/science/article/pii/S0003267098006163#aep-abstract-id14.

For this article the wavelengths are 200 and 300 for nitrate. The other thing is that it states that it is used for wastewater and in industrial applications; it does not specify the type of water what could be in seawater.

it can be used possibly by doing serial dilution process