I haven't the slightest idea, so am qualified to make guesses!
To me it looks like the rescue of men from a ship's lifeboat, or else a local small boat, by a larger ship. It doesn't look like an RNLI lifeboat. From this I'd deduce that it either represents one specific, probably heroic, rescue or else it is a memorial to men being rescued in general - perhaps WWI or WWII?
Am I anywhere near?