The shortlist includes Youssef Ghali from Egypt; B & C Associati from Italy; Arca from Manchester; and London's Chris Curtis & Elliott Wood, Hakes Associates, and Softroom.
RIBA adviser Renato Benedetti said: 'We were delighted with the energetic response to the competition. The 88 entries showed a wide variety of approaches and solutions and the shortlist is interestingly diverse.
'We are looking forward to meeting the six shortlisted architects for the interview stage and selecting the winner.'
The improvement to the Leeds to Liverpool canal corridor is desperately needed. The site is a particularly rundown area of Bootle, one of the most dilapidated parts of the city.
Sefton Council member Lee Payne said: 'The interest in the competition has been amazing and really shows that the regeneration of south Sefton has captured the imagination.
'Choosing between the 88 designs was very difficult and is testament to the hard work put in by those who submitted entries.'
The remaining practices will battle it out in a competitive interview on 8 February.