Hiya
Just curious as to WHY you want to stick to the 1nm limit? A single engine boat, with a vhf radio and some safety kit, allows you to fish up to 5nm from shore.
Having a small boat and only operating 1nm from shore is going to SEVERELY limit your fishing in the Gordons bay area. In summer, the inshore reefs offer good geelbek and cob, but other than that, its pretty dead. You will need to be able to travel a bit further out for decent bottom fish. The Maccassar area is particularly good for bottom fish and you are fishing less than 1.5nm from shore. It is how-ever 7-8nm from the harbour, but you are at all times travelling about 1-2nm from the shore.
Your SJ410 will comfortably tow and retrieve a variety of small boats. The lightest and safest bet would be a small semi-rigid inflatable, something like a 3.8m to 4.3m boat. Powered with a 15-30hp sized engine, it will be VERY economical. SHould you want to venture futher afield, Sir Lowry's Pass is going to be a problem with the SJ410. Rather opt for the more scenic Gordans Bay to Hermanus road. This way, you miss Hou-hoek pass, which has a steep climb on your return journey.
Price ranges from R5000 to R25000 for a decent set-up.
If you still want to only fish 1km from shore, Dorado75 has the perfect vessel for you!!
Regards
miles