Powerful swimmer looks after hospital ship (5,5)

I believe the answer is:

nurse shark

'powerful swimmer' is the definition.

'looks after hospital ship' is the wordplay.
'looks after' becomes 'nurses' (I've seen this before).
'hospital' becomes 'h' (abbreviation for hospital on maps).
'ship' becomes 'ark' (I've seen this in other clues).
'nurses'+'h'+'ark'='NURSE SHARK'

I've seen this clue in The Independent.

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