Nah, I can't see Clive being any good at people smuggling - as is evidenced by them being caught...
Clive being in with the sort of people who are involved in people smuggling/drugs, on the fringes, and thus being able to borrow/acquire a boat - yes. And then once living illegally on a boat in the Caribbean... even more so.
He's too much of a loud mouthed idiot though to be any sort of big cheese/organiser... he's someone who some fool has trusted to do the donkey work, way way way down the bottom of the chain. Manual labour.
I think the whole 'baby on a beach' was them avoiding UK SS... as they've got a ton of past history with them and concerns for their child/children.
And then the botched attempt at people smuggling was a desperate act to raise money that they'd badly need - maintaining a boat, even there, and even where you cut all corners, don't pay mooring fees etc... is spendy AF and so is keeping it stocked with food/water etc.
I hadn't realised/had forgotten that the older child is also Iulias - that is a long gap between kids... are there other kids that have been removed? I guess we won't know.
Makes more sense she'd risk a freebirth having given birth before though. It also makes it a bit less likely that she's naive and clueless - she could still be being co-erced by Clive... but I don't really buy that. I think she's in it up to her neck as much as he is.