Non-Air Shipping UK to USA

[veevee]

Advice needed: I need to send a box approx 80x80x50cm, 15kg. to the USA, cannot be sent by air. Value isn't especially high so it wouldn't be worth spending much more than £100 on shipping. Can anyone point me in the right direction?

Thanks in advance!

[veevee]

Shipping restrictions, it can't go by air.

[veevee]

Laser toner cartridges, pretty sure these can't be shipped by air in any way, though.