But after a tense few seconds their looks of concern relax into smiles – just as a waitress gleefully whisks us away.
To call Deep Blue a ‘fish and chip restaurant’ seems reductive. Being suspended directly above the sea puts it in unrivalled stead, but swing open its doors and what’s inside is surprising.
It’s vast, bright and airy – a far cry from some of the salty shacks anyone who grew up in a seaside town or city will be familiar with.
The finish is modern and open-plan and there’s a well-stocked bar looking out on to a wealth of seating.
Our spot is a cosy booth which would have boasted a nice view of the pier and the coastline, had it not been dark outside.
To get started I opt for a pint of the Goose IPA on tap. Fittingly it’s citrusy – and lively with carbonation – but some of that goodness is dampened by its £5.20 price tag. I’m a long way from the greasy chippy down the road now.
Any awkwardness we experienced upon arrival is remedied by our waiter. He is polite and funny – and the fact he takes our orders without using a pad and pen doesn’t go unnoticed.
Thankfully his memory doesn’t fail him and after 15 minutes or so our mains arrive .
I go for wholetail scampi served with chips, mushy peas and tartare sauce – a staple when done well (£10.99).
My companion meanwhile puts Deep Blue’s vegetarian options to the test and chooses the battered halloumi burger, also with chips (£12.99).
As we indulge, our plucky waiter returns and asks: ‘Is the food as bad as the service?’ Thankfully, it was just as good.
Dipped in tartare sauce and smattered with lemon juice, the scampi is tangy, hot and perfectly moist beneath its breadcrumb shell. And with nine or 10 pieces to boot I was not left wanting.
The chips are slightly greasy, like a chip shop’s, unsurprisingly, but were tasty. The mushy peas are mushy peas as they should be.
Across the table my opposite number is making all the right noises. They offer me a bite of their burger. I accept.
Given it is battered, this flavoursome halloumi burger packs more of a crunch than a squeak and – throwing caution to the modern trend of sliver-serving – comes as quite a chunk.
If you’re a herbivore after a hearty burger to fill you up, you won’t go wrong with this.
The dessert menu is short and simple.
I choose the warm chocolate fudge cake with fresh cream (£4.99) – breaking the beige trend we’ve been following since we arrive.
My dining companion goes for a crème brûlée (£5.99).
The chocolate is rich and the cake soft, but I’m not sure if it is homemade.
The brûlée, I am told, is very sweet.
It comes served in a cocktail glass, in case you are wondering, which suggests it has been lovingly made on-site.
Sadly I am not offered a bite of this course – but that must be a good sign.
If you’re after vivid colour and an exotic garnish from your coastal cuisine Deep Blue may not be for you.
But if you do fancy fresh fish and chips and a sit-down – away from Portsmouth’s bullish gulls and gales – there’s no reason not to pay it a visit.
Even if you’re in a hurry, the restaurant has a takeaway arm on the side.