D24T oil leak

[Ian47]

Hi, I have D24T in my boat, there is an oil leak at the front of the engine. It is very difficult to access the area in order to identify the cause. The oil can be seen running down behind the timing gear back plate just below the water pump.
I replaced the front crankshaft seal last year and the rocker cover gasket twice, the last time I used instant gasket at the front and rear joints.
My question is:- Is there anything other than the front camshaft seal that could cause a leak? I replaced the timing belts and tensioner when I did the crankshaft seal.
I assumed that as the oil wasn't being thrown out the seal would be OK, but it seems the only thing left.