of the limit of 80 would be increased to 200. but while cerb (smallest deep water ship would have 225BR it still could not enter a shallow pb)
The BR is in place because player were able to teleport deep water ships into shallow water via tows. and therefore would made them able to join those battles.
Imagine a defender would tow his trincs or whatever to nassau while the attacker is around in mercs. Furthermore sometimes the PB join circle can overlap into deep water should 1st join because of that?