ACROSS

 6.   Item of dried fruit, but doesn’t always assist your motion (7)
7.  Vessel, for air or a piston (8)
9.  In Majorca, it does not taste quite how it should (5)
10.  Chopping gesture, the signs don’t look good (3,2,3)
14.  Junk thrown over the side of a boat (6)
18.  If you don’t lose it, you might find one on a dive (6)
19.  Don’t drive your boat over one of these! (4)
21.  Betting shop, popular with fish (5)
22.  You must pay for the fish when it arrives! (3)
23.  Leg attire, feared by divers (8)
26.  Diver after too long in the sun (7)
27.  Better not land in it (unless you’re going diving) (5)

DOWN

1.  Both boats and whisky can be found on them (5)
2.  Better not do this to yourself or your sorrows (5)
3.  A handy mollusc, also an air source (7)
4.  Junk from a shipwreck (7)
5.  The flashing blade (5)
7.  Goes with ‘neck’, ‘wax’ and ‘turn’ (6)
11.  Most divers wear this stuff...dogs like it too! (6)
12.  Let there be light! (5)
13.  A serious part of the boat (5)
14.  Weird invertebrate, not available in fruit flavours (9)
15.  Used by divers, climbers and weightlifters (4)
16.  Diving accessory featured in ‘Arabian Nights’ (6)
17.  A person, a bird, a magazine (5)
20.  Bigger version of (12), also available in Chinese type (7)
24.  Better go to the leeward site to do this (4)
25.  Part of a boat, nothing to do with arrows (3)