Large swimmers requesting quiet aboard ships (7,6)

'large swimmers' is the definition.
'basking sharks' can be an answer for 'swimmers' (basking shark is a kind of aquatic vertebrate). I am not sure about the 'large' bit.

'requesting quiet aboard ships' is the wordplay.
'requesting' becomes 'asking' ('ask' can be a synonym of 'request').
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'aboard' becomes 'barks' (I can't explain this - if you can you should give a lot more credence to this answer).
'ships' is an insertion indicator (to ship can mean to carry or transport something).
'asking'+'sh'='askingsh'
'askingsh' inserted into 'barks' is 'BASKING SHARKS'.

Can you help me to learn more?